Historical Context and the Origins of IPT

The decade of the 1960s, in the United States and Western nations around the world, represented a crossroads between old and new, and was a period in history that bridged paradigm shifts in social, political and interpersonal relationships. The post–World War II period had ushered in a time of peace and prosperity in the United States that laid the foundations for loftier goals of improving material conditions that contribute to poverty, illness and racial discrimination (‘The Great Society’). Programmes that supported post-secondary education, job training, transportation infrastructure and increased access to healthcare were established to promote a higher quality of life for lower- and middle-income families. The social and economic mobility for working class white Americans, many the children and grandchildren of immigrants, was steadily improving; and so did expectations for subsequent generations’ educational, occupational and social prospects. The space programme and the governmental funding for science and technology to explore the world beyond our planet and land on the moon was a first in the history of human beings and spoke to the general momentum for change, innovation and expectations for what could be achieved. This was a time ripe for transition, with the innovations of science and technology increasing individuals’ expectations for a high quality of life. These innovations, evidenced by the advent of vaccines that decreased rates of childhood diseases and improved infant mortality rates, and the wide-spread use of the birth control pill that expanded women’s reproductive freedoms, spurred social change that affected every level of society. While this overall period of economic and political stability forwarded programmes of sweeping reforms, it stands to underscore that progressive social change was only beginning as, across the world, social movements galvanised to address systemic racism and highlighted the underbelly of continued imperialism/colonialism during the Cold War.

The burgeoning field of psychiatry experienced the same types of transitions and innovations and benefitted from governmental investments to further new developments in healthcare and science. At this time, American psychiatry lacked a clear identity and direction and was a field of practice that was open to reinvention. At the turn of the twentieth century, American psychiatry grew out of the European tradition of treating mental disorders in institutionalised settings and outpatient treatment was heavily influenced by psychoanalysis. Inpatient settings that provided care were the first settings where psychiatric research was conducted nosology or classification of mental disorders, aspects of research that led to the development of the Diagnostic and Statistical Manual of Mental Disorders (DSM). Early psychopharmacology trials for serious mental illnesses such as schizophrenia, expanded the knowledge base of psychiatry and increased the use of psychiatric medications to treat conditions such as psychosis, bipolar and depressive disorders and anxiety.

Nothing was known about the efficacy of psychological therapy, which was not systematically integrated into psychiatric care in institutions until the post-World War II era. Psychoanalysis was not widely disseminated and accessible as a part of routine healthcare. It gained a foothold in large cities, such as New York, was the domain of individual providers who had close training ties to Freud and his first-generation of students. As a treatment modality, psychoanalysis was accessible only to the wealthy. As the field of psychiatry expanded, the psychoanalytic tradition was integrated into ambulatory treatment settings and influenced assessment (i.e., the Rorschach) and intervention. There were no clinical trials of any psychotherapy, with the prevailing belief that psychotherapy could not be studied because every clinical case was unique. However, a competing current of innovation in the field of psychiatry was taking place in the seminal studies on learning and behaviour conducted by pioneers John Watson and B. F. Skinner. Although built upon the foundational studies of Ivan Pavlov, behaviourism was a school of psychology that was culturally synchronous with American themes popularised after World War II, such as self-determination and freedom of opportunity. American behaviourism as a treatment modality also stood in stark opposition to psychoanalysis, with its focus on the present instead of the past, on symptom reduction as opposed to insight, and with short-term, time-limited treatment replacing time intensive, long-term analysis. The type of psychological therapy presented by behaviourism was also something more accessible to Americans, making it less of a ‘black box’ than psychoanalysis. Still, the idea of research on psychotherapy faced significant opposition due to a prevailing belief that psychological therapy could introduce non-meaningful variables in psychiatric treatment. One of the first studies focused on the outcomes of psychological therapy (but not a randomised clinical trial), published by Hans Eysenck, cast doubt upon the success of those receiving psychoanalysis and concluded that most clients’ psychiatric symptoms resolved independently and without psychological treatment [Reference Eysenck1]. This paper, later retracted, contributed to trends of minimising the effects of psychological intervention and reducing the focus on studying the efficacy of psychological interventions.

Many elements of behaviour therapy, especially Skinner’s operant conditioning, were translated into contingency management programmes or token economies that began to be implemented in institutional settings. Beyond this, behaviour therapy introduced ground-breaking ideas about the implementation and dissemination of psychological therapies, specifically the ideas that treatment could be manualised, that the techniques used by therapists were the mechanisms for changing symptoms rather than transference relationships and that providers could learn how to conduct treatments without apprenticeships or going through their own psychoanalysis. Ellis’ Rational Emotive (Behaviour) Therapy was one of the first manualised approaches to outpatient behavioural therapy [Reference David, Cotet, Matu, Mogoase and Stefan2]. Still, the practice of behaviour therapy seemed to lack a key interpersonal experience for many providers and clients. While therapists were no longer blank screens to capture and magnify transference issues, they were now more pedantic, direct and rational. This systematic approach to psychological therapies experienced some backlash by academics and providers who viewed its generalised perspective on disorder and manualised approach as discounting the uniqueness of individual’s experiences and as potentially de-humanising. The rise of Carl Rogers’ work on personality development and psychological therapy, Client Centred Therapy, evolved as an alternative to both prevailing models of outpatient treatment, psychoanalysis and behaviourism. Rogers’ theoretical and practical contributions to psychological therapies focused heavily on the therapeutic relationship and in identifying techniques and methods that build interpersonal foundations between providers and clients that facilitate growth, progress and change [Reference Rogers3, Reference Rogers4]. Client-centred approaches to psychological therapy also sought to de-stigmatise mental health treatments and popularised the idea of using psychological therapy as an additional approach to building mental wellness, self-growth and self-actualisation. These themes resonated with progressive social movements that challenged traditional societal hierarchies and structures that maintained militarism, paternalism and racial and gender discrimination and echoed the belief that mental health, like society, could change. The primary drawback to the humanistic psychology movement was an anti-research stance that served to ‘re-mystify’ the process of psychological therapy. Aligning research on psychological therapy outcomes as reductionism and de-humanising thwarted process research and delayed the study of therapeutic techniques that were introduced by Rogers and his colleagues. Unlike Eyesenck’s paper, some of the first studies of psychological therapy highlighted the importance of the therapeutic relationship as a potential mechanism for positive outcomes for treatment. However, it is important to note that these studies were not clinical trials, with random assignment, inclusion of a control or comparator treatment and careful description of the treatments being tested. Towards the close of the 1960s, there was increasing heterogeneity in the field of outpatient psychological therapy that set the stage for the emergence of evidenced-based psychological therapy models, such as IPT.

Biographical History of Gerald Klerman

The history of IPT would not be complete without the biography of Dr Gerald (‘Gerry’ to his friends and family) Klerman. Dr Myrna Weissman, co-developer of IPT and Klerman’s wife, has served as the primary resource on the history of IPT since Klerman’s untimely death in 1992 [Reference Weissman5–Reference Markowitz and Weissman7]. At the time of writing this chapter, Weissman was Diane Goldman Kemper Family Professor of Epidemiology in Psychiatry at the College of Physicians and Surgeons and Mailman School of Public Health at Columbia University and was Chief of the Division of Translational Epidemiology at the New York State Psychiatric Institute. In conversations over Zoom, through emails and comments on this chapter, Dr Weisman shared with us memories of her late-husband and her first-hand perspective of how their collaborative research shaped the field of psychological therapies and psychiatry.

In many ways, Dr Klerman’s story is one that is distinctly American: he was the son of an immigrant father from Russia and an American-born mother who grew up in a close-knit, working-class family with his younger sister, Jean, on the Upper East Side of New York City. Born in 1928, young Klerman was smart, intellectually curious and hard working. His parents encouraged his academic achievement and supported his trajectory towards science and medicine. Klerman attended The Bronx High School of Science (‘Bronx Science’), a competitive public high school in New York, and excelled there. He was already establishing himself as an academic, gravitating to debate and ‘playing with ideas’. He was accepted to Cornell University and graduated in 1950, and then attended New York University (NYU) School of Medicine, graduating in 1954. During medical school, Klerman sought out additional studies in sociology and began to integrate ideas of social risk factors into his understanding of disease processes and human behaviour. It was in medical school that he began pursuing his life’s passion, the scientific study of psychiatric disorders. During his residency at Massachusetts Mental Health Center in Boston, Klerman trained as a psychoanalyst, a standard training rotation for psychiatrists. Although Klerman ‘flunked’ as an analyst, he had great respect for his supervisors and the field of psychotherapy and subsequently charted a career course better suited to his strengths, research on pharmacology for severe psychiatric disorders such as schizophrenia. At the onset of the Korean War, the newly minted Dr Klerman was accepted as a member of the unfortunately titled, ‘Yellow Berets’ at the National Institute of Health (NIH) [Reference Khot, Park and Longstreth8]. There was a pressing need for physicians with the war and many were being drafted into service. The best and the brightest minds were recruited to be trained to conduct research, establish new treatments and provide care at the NIH. Like Klerman, each new appointee completed two years of clinical training before arriving at the NIH. Their primary responsibility was learning how to conduct basic or clinical research under the guidance of a senior scientist. The second job was to care for clients at the NIH Clinical Center. Klerman trained and participated in the first treatment studies evaluating the efficacy of pharmacology for the treatment of schizophrenia. His time with the Yellow Berets was immensely productive –there he became a ‘well-trained scientist’ in addition to a skilled psychiatrist. Klerman’s first job, post residency and wartime service, was as the Director of Yale University’s first community mental health centre, where he started in 1966.

Development of Interpersonal Psychotherapy

In 1969, Klerman was the head of the Connecticut Mental Health Center and was faculty at the Yale University School of Medicine. Dr Euguene Paykel, a young psychiatrist from London, joined Klerman as a postdoctoral fellow at Yale University and worked under Klerman in designing a clinical trial to examine effects of tricyclic medication in maintenance treatment for individuals with unipolar depression. At the time, tricyclic medications represented the state of science treatment for depression, but psychoanalysis or psychotherapy were the primary treatment modalities that clients received. Although the idea of combination treatment with medication and psychological therapy is obvious to the contemporary reader, the additive effects of combination treatment seemed less clear in 1969. It was unclear if psychological therapy, particularly psychoanalysis with its focus on making unconscious conflicts conscious, would increase client distress and cancel out any positive gains from medications. Similarly, it was unclear if symptom reduction achieved with tricyclics would decrease client motivation or engagement needed for a successful course of psychological therapy. As a postdoctoral fellow, Dr Paykel was a healthy sceptic about the role of psychological therapy in the maintenance treatment for depression. Klerman, as the senior investigator, was unsure psychological therapy would demonstrate a treatment effect but felt strongly that psychological therapy should be included in the maintenance trial for two primary reasons: (1) most clients in real-world clinical settings received psychological therapy and Klerman wanted the components of this clinical trial to reflect and inform actual practice and (2) psychological therapy could and should be studied as systematically as medications for the treatment of depression and other mental disorders. To date, there had not been any randomised clinical trials of psychological therapy and Klerman saw the maintenance study of depression as an initial step towards this end. The most important motivation for including psychotherapy in the maintenance treatment of depression study was that the National Institute of Health (NIH) would not fund the project without including a psychotherapy arm. NIH reviewers wanted to learn about the effects of medication and knew that, in the real world, many clients would be receiving psychotherapy of some kind along with medication or alone. This external demand increased concerns that psychotherapy, delivered in a non-systematic manner, might undermine and confound any potential medication effect.

IPT was developed as the time-limited, ‘high contact’, supportive treatment that would be included as the proxy for psychological therapy in the maintenance trial. Klerman, along with Weissman, Paykel and Brigette Prusoff, a biostatistician, comprised the team tasked carrying out the study. Klerman and Weissman were to operationalise the psychological therapy condition so it could be delivered by study therapists in a systematic manner, with clear procedures and defined interventions. Their goal was not to create a new model of psychological therapy but to assemble best practices observed from clinical experience and from the expert providers [Reference Weissman6]. ‘Our intent was not to develop a new psychotherapy, but to describe what we believed was reasonable and current practice with depressed clients and might be considered for inclusion under the rubric of short-term psychotherapy’ [Reference Klerman, Weissman, Rounsaville and Chevron9]. However, their construction of psychotherapy was unique in several ways. First, depression was conceptualised from both a medical/disease model and as related to life events/experiences. As Klerman reflected at the time, ‘One of the great features of the brain is that it responds to its environment’ [Reference Weissman5]. Second, interpersonal relationships were highlighted as important and stem med from the types of life events that often contributed to the onset or relapse of a depressive episode. The focus on interpersonal relationships in psychological therapy was not new; however, the focus on concurrent relationships and their influence on the onset of depression in the individual was a deviation from psychoanalysis’ emphasis on early childhood experiences and emerging personality. It also brought attention to the role of social support as a protective factor in managing chronic and episodic mental disorders, observations noted by community providers and those working closely with clients. Lastly, IPT was both a time-limited and manualised psychological therapy, two aspects that were novel for the time. There were many books on psychotherapy available, however, treatment manuals were different in that their aim was to train psychotherapists for clinical trials with methods that were systematically described. At the time, most models of treatment, especially for mental disorders of a recurrent nature, involved long-term psychological therapy such as psychoanalysis. A manual for psychotherapy, in contrast, was comprised of the actual language used to carry out a particular therapeutic procedure or technique, in addition to directions about structuring sessions and identifying content for psychoeducation, affective expression and skill development. The idea of a manualised treatment was unheard of at the time and resisted by psychoanalysts and client-centred therapists for fear of reductionism and de-humanising clients. However, manualising procedures and interventions for psychological therapy was consistent with behaviourism. Around the same time, Aaron Beck, a Professor at the University of Pennsylvania, began writing the first manual for cognitive therapy for depression. It was not a coincidence that what would become later known as cognitive behaviour therapy (CBT) and IPT shared a similar timeline in their origins, as the development of manualised treatments for depression was a state of the science necessity for moving research on the efficacy of psychological therapy forward. Beck and Klerman were contemporaries, and also friends.

Klerman and Weissman agreed on key components that would be systematically utilised in the psychological therapy condition, including psychoeducation which included informing the client of their diagnosis and treatment options, a timeline for identifying the onset and manifestation of symptoms along with other developmental transitions and life events, and an interpersonal inventory of all significant relationships with family members, partners/ spouses, friends, peers and children. They agreed that psychoeducation about depression would be presented from the medical model to reduce self-blame and encourage self-care through meeting legitimate needs for help and temporary respite from responsibilities in a time of illness.

A significant addition to the treatment would be a clinical formulation that could be easily understood by clients and could organize treatment. This formulation would be collaborative and would come after a process of linking symptoms to changes in interpersonal relationships or interpersonal events and culminate in the selection of one of four problem areas which they chose and defined because of their association with the onset of depression. The problem areas were grief, role transitions, role disputes and interpersonal deficits, which were associated with the onset of recent symptoms and would frame and define the goals of the short-term psychological therapy.

As the research group was identifying and constructing treatment parameters, they also invested time and thought in ways of measuring outcomes and efficacy of early IPT. While it was unclear if psychological therapy could reduce symptoms of depression, Klerman and Weissman hypothesised that psychological therapy could enhance the social functioning of clients with depression, that could indirectly improve and maintain symptom stability. However, there were no assessments of social functioning available that assessed multiple domains (i.e., employment/work, sex and dating, family relationships, relationships with children) and included work done by women not employed outside of their homes. All these areas were considered important to assess in the clients consisting of mostly in the maintenance of depression clinical trial who were mainly married women with children. This perspective was important in motivating Weissman to develop and validate the Social Adjustment Scale (SAS). It was first used as an interview, and she later adapted it as a self-report measure of social adjustment (SAS-SR). This measure is still used to capture changes in functioning in social situations such as work, relationships with family and friends and romantic relationships, and importantly keeps the focus of psychological therapy very pragmatically grounded in behaviour change.

The results of the Maintenance Study of Depression [Reference Klerman, Dimascio, Weissman, Prusoff and Paykel10], published in 1974, came as a pleasant surprise to Klerman and the IPT group: clients receiving tricyclic medications (e.g., amitriptyline) were more likely to avoid relapse after eight months of treatment, and those receiving ‘high contact’ psychotherapy demonstrated improved social functioning [Reference Klerman, Dimascio, Weissman, Prusoff and Paykel10]. This finding was instrumental in moving the development of IPT forward and contributed to the burgeoning field of randomised clinical trials for psychological therapy. Utilising the same framework for demonstrating efficacy in psychiatric medications, Klerman pushed for another trial to examine the replicability of outcomes. The second study of IPT, led by Weissman, compared the efficacy of medication alone, IPT alone and combination treatment (e.g., medication and IPT) in the acute treatment of adults with depression. Results indicated that IPT and medications had equal efficacy and combination treatment was more effective than either medication or IPT alone [Reference Weissman, Prusoff, Dimascio, Neu, Goklaney and Klerman11]. These early studies of IPT were instrumental in having NIMH initiate the multi-centre Treatment of Depression Research Program [Reference Elkin, Shea, Watkins, Imber, Sotsky and Collins12, Reference Elkin, Parloff, Hadley and Autry13]. This was the first large randomised controlled trial to examine the comparative efficacy of two emerging evidence-based psychotherapies, IPT and CBT. The three sites chosen for this clinical trial, George Washington University (Washington, DC), University of Pittsburgh (Pennsylvania) and University of Oklahoma, were not sites where CBT or IPT had been developed and represented the first, best test of implementation and validation by therapists with no history in the development or investment in either therapy modality. The results from this study concluded that IPT and CBT performed similarly well as primary interventions for depression. However, IPT differentiated itself from CBT in three ways: (1) in the overall sample, IPT was more effective than placebo and case management in the treatment of depression, whereas there were no differences between CBT and placebo/case management, (2) both IPT and medication/case management demonstrated superior recovery rates for depression and (3) IPT demonstrated some efficacy with the most severely depressed and impaired clients, compared with the placebo/case management and CBT treatment conditions [Reference Elkin, Shea, Watkins, Imber, Sotsky and Collins12, Reference Elkin, Parloff, Hadley and Autry13]. Furthermore, IPT was superior to medication in increasing social functioning in depressed clients at post-treatment assessment. This study was seminal in providing the independent validation/replication of IPT to establish it as an evidence-based treatment, and it also suggested that IPT conferred some treatment benefits for clients who were more severely depressed.

Disseminating IPT and Expanding Training and Research Internationally

The history of training therapists and disseminating IPT as a psychological therapy available to clients outside of clinical trials research grew from both academic teaching delivered by IPT researchers in university medical centres and community therapists discovering IPT. With the publication of Klerman, Weissman and colleagues’ 1984 book, Interpersonal Psychotherapy for Depression [Reference Klerman, Weissman, Rounsaville and Chevron9], there was an increased demand for additional training from university based IPT researchers. The IPT manual has been regularly updated by Weissman, and Klerman’s name as co-author has been retained after his untimely death in 1992 [Reference Weissman, Markowitz and Klerman14, Reference Weissman, Markowitz and Klerman15]. After the success of the NIMH Treatment of Depression Research Programme, the propagation of research and training in IPT was clustered at two primary sites in the United States: at the Cornell School of Medicine and Columbia University/New York Psychiatric Institute (NYPI), where Drs Klerman and Weissman relocated (respectively) in 1987, and at Western Psychiatric Institute & Clinic (WPIC) in Pittsburgh, Pennsylvania, under the direction of Drs David Kupfer and Ellen Frank. IPT thrived in these academic homes and became routine part of the training experiences of psychiatry residents and clinical psychology interns and postdoctoral fellows, while launching the second generation of IPT researchers who in large measure stayed within the same institutions, most notably Drs John Markovitz, Laura Mufson, Michael O’Hara and Holly Swartz. Although the interest in IPT went beyond these two medical centres, it was often difficult for practitioners to access training in this treatment model.

How did IPT migrate across the globe? Drs Klerman and Weissman collaborated internationally in their research programmes outside of IPT. It is important to remember that Weissman’s career did not revolve around IPT, as she is an internationally renowned epidemiologist who conducted the first population studies of psychiatric disorders using clinical diagnosis [Reference Weissman, Bland, Canino, Faravelli, Greenwald and Hwu17, Reference Weissman, Sholomskas, Pottenger, Prusoff and Locke18] and ground-breaking research on the intergenerational transmission of depression in families [Reference Weissman19, Reference Weissman, Wickramaratne, Nomura, Warner, Pilowsky and Verdeli20]. These studies have been so important that they charted paths for new technologies and approaches that will further inform the field of psychiatry’s understanding of risk and mechanisms for mental disorders in individuals across the lifespan [Reference Weissman and Talati21, Reference Weissman, Talati, Hao and Posner22]. Weissman has won many lifetime achievement awards. In 2009, she was selected by the American College of Epidemiology as one of 10 epidemiologists in the United States who has had a major impact on public policy and health. In 2021, Weissman received the research award from the American Psychiatric Association, followed by receiving an award for her research on mood disorders from the American College of Psychiatrists in 2023. Hence, it was particularly impressive that Weissman continued to promote the study and dissemination of IPT after Klerman’s untimely death in 1992. Weissman was seminal in developing and implementing the first clinical trial of group IPT in Uganda, Africa [Reference Bolton, Bass, Neugebauer, Verdeli, Clougherty and Wickramaratne23–Reference Bass, Neugebauer, Clougherty, Verdeli, Wickramaratne and Ndogoni25], work that included colleagues Dr Lena Verdeli and Kathleen Clougherty, LCSW, who are now established researchers and trainers in implementing global mental health models of IPT. This work also brought IPT to the forefront of the World Health Organisation (WHO) and in 2016 Weissman and Verdeli published their group IPT manual [26]. This WHO manual remains a pivotal achievement in the history of IPT, providing this intervention to an international audience and as a model for training both mental health and community health providers in low and middle income countries (LMIC). In this manner, IPT re-emerged as a psychological intervention that could be disseminated and scaled to reach individuals in settings that would typically not have access to evidence-based, mental health treatment.

Dr Paula Ravitz, a professor and former Morgan Firestone Psychotherapy Chair in the Department of Psychiatry at the University of Toronto, contributed to the propagation of IPT in North America, the United Kingdom and Europe through her expertise as a clinical educator and through developing new platforms for online training of mental health therapists in evidence-based treatments in Canada (www.coursera.org/learn/learn-ipt). Dr Ravitz was interviewed via virtual meetings and through working on the Forward for this book about her role in expanding the training and implementation of IPT in North America and in the United Kingdom. In 1995, Dr Ravitz arrived at the University of Toronto School of Medicine to complete her psychiatry residency and completed training in Interpersonal Psychotherapy, at the IPT Clinic, housed in the Centre for Addiction and Mental Health and directed by clinical psychologist Dr Laurie Gillies with occupational therapist Dr Edward McAnanama, PhD, who had received training in IPT from American psychologist, Dr Cleon Kornes, a member of the clinical team in the NIMH Study of Depression Research Collaborative Program at the University of Pittsburgh site. Ravitz was intrigued by this model of psychological therapy and sought additional training by attending workshops on IPT in both New York and Pittsburgh. She approached Dr Ellen Frank at the University of Pittsburgh, who agreed to supervise her implementation of IPT with actual cases. Ravitz remembered being grateful for this degree of collaboration and recalled mailing ‘cassette tapes of sessions’ to Frank and having ‘phone supervision’ sessions. The IPT Clinic at the University of Toronto and CAMH began to garner attention in the United Kingdom as a training site for psychologists interested in IPT. In 1996, a small group of psychiatrists and psychologists from the University of Edinburgh, including Drs Roslyn Law and Anthony Bateman, trained with Dr Gillies and Dr McAnanama in Toronto, and were established as IPT trainers. Many in this group were responsible for the first randomised clinical trial of IPT in the United Kingdom [Reference Power and Freeman27]. After accepting a position with the CAMH in 2000, Dr Ravitz became Head of the Interpersonal Psychotherapy Clinic and began hosting annual two-to-three-day training sessions in IPT as she became increasingly focused on conducting outcome and process research on IPT with psychologist Dr Carolina McBride. These workshops were among the earliest offered to therapists outside of New York and Pittsburgh and attracted psychiatrists and psychologists across North America and Europe. Ravitz co-led the first IPT training workshop with Kathy Clougherty, LCSW, offered at the inaugural International Society for Interpersonal Psychotherapy (ISIPT) conference in Pittsburgh in 2004, further establishing her prominent role and excellence as an educator and trainer in IPT. To date, Dr Ravitz has co-led outcome research on the effectiveness of telephone delivery of IPT for perinatal depression [Reference Dennis, Grigoriadis, Zupancic, Kiss and Ravitz28] and process research projects, focusing on moderators of IPT [Reference Bernecker, Coyne, Constantino and Ravitz29–Reference Constantino, Manber, DeGeorge, McBride, Ravitz and Zuroff32]. She has co-authored a meta-analysis on IPT and authored a scoping review on the history of IPT research and implementation [Reference Ravitz, Watson, Lawson, Constantino, Bernecker and Park33]. Dr Ravitz’s expertise also focuses on knowledge exchange and strategies for adapting, implementing, teaching and disseminating IPT [Reference Ravitz, Cooke, Mitchell, Reeves, Teshima and Lokuge34–Reference Ravitz, Heeney, Lawson, McAnanama, Pain and Kiss36], some focusing on under-resourced communities across the globe, including rural communities in Canada, and for task-shifting projects in Ethiopia, with Toronto Addis Abba Academic Collaboration (TAAAC) leads Drs Dawit Wondimagegn and Clare Pain [Reference Ravitz, Wondimagegn, Pain, Araya, Alem and Baheretibeb35, Reference Wondimagegn, Hailu, Ravitz, Pain, Weissman and Mootz37]. Dr Ravitz has been instrumental in training and disseminating IPT through her many workshop trainings, her co-edited educational book/video series, Psychotherapy Essentials to Go, and as the first author of a book in the series on Interpersonal Psychotherapy for Depression [Reference Ravitz, Grigoriadis, Watson, Ravitz and Maunder38] and, most recently, launching of an eight-hour asynchronous online open-access IPT training course through Coursera (www.coursera.org/learn/learn-ipt). Most recently she piloted and launched open-access online IPT training with a nine-hour asynchronous case-based, interactive IPT course through Coursera (www.coursera.org/learn/learn-ipt).

The migration of IPT to the United Kingdom was truly a watershed moment in the dissemination of the treatment as IPT was scaled for implementation in the UK unlike anywhere in the world. A small core of IPT trained psychologists founded IPT-UK, an organisation of diverse mental health professionals who were committed to training and disseminating IPT in England, Scotland, Northern Ireland and Wales (www.iptuk.net). They created a collaborative for sharing ideas, offering training and supervision in IPT and standardising measures for assessing trainees’ competence and fidelity to IPT. However, training mental health providers across England in IPT was greatly facilitated in 2008 by the Improving Access to Psychological Therapies (IAPT) programme (now known as Talking Therapies), a government-funded initiative to create and centralise IPT training in England. IAPT provided the resources, structure and systematic training that allowed a large number of mental health professionals, many working for the National Health Service (NHS), to be certified in the provision of IPT [Reference Law, Duffy, Weissman and Mootz39]. Despite funding changes that required the de-centralisation of training efforts, regional training programmes in Scotland, Northern Ireland and Wales, and larger training institutions in England have continued to disseminate and train mental health providers in IPT across the United Kingdom. The IAPT programme has funded centralised training in England in Interpersonal Psychotherapy for Depressed Adolescents (IPT-A) since 2012, significantly investing in the training of mental health providers’ ability to deliver evidence-based psychological interventions to depressed young people. As of February 2024, there were approximately 1,000 trained and certified IPT therapists in the United Kingdom.

State of the Science and the Status of IPT

So where does IPT sit in the structured evidence base of psychological treatments almost 50 years later? There is no doubt that IPT has a place at the table of evidence-based psychological interventions for depression in adults [Reference Ravitz, Watson, Lawson, Constantino, Bernecker and Park33], and that its adaptations in different age groups, such as IPT-A [Reference Mufson, Pollack Dorta, Moreau and Weissman40], different clinical populations such as peripartum depression [Reference Bright, Charrois, Mughal, Wajid, McNeil and Stuart41] and different psychiatric disorders such as Interpersonal and Social Rhythm Therapy (IPSRT) for bipolar disorder [Reference Crowe, Beaglehole and Inder42], have consistently built upon and expanded the body of research supporting the efficacy of IPT. It is also true that IPT has been identified as a first-line treatment for depression by the WHO and has informed global mental health initiatives [26]. However, it is also safe to say that IPT has not experienced the widespread dissemination seen with CBT, which has dominated the training of psychiatry residents, psychology trainees and social work interns (in the United States). In documenting its history, it is important to consider how the dissemination of IPT was shaped by several events, such as the premature death of Dr Klerman, its academic home in two prominent medical centres in the United States and the shift in research funding priorities at the NIH in the United States that reduced the focus on psychotherapy research.

In 1992, Dr Klerman died unexpectedly at the age of 63 due to complications from an illness. In many ways, Klerman was at a time in life when his attention could have turned towards increased mentoring, teaching and creating a legacy for IPT that would survive him. His death left a void in his family, in the field of psychiatry and possibly in the propagation of IPT. At the time of his death, the second generation of IPT researchers, most of whom were either trained by Klerman directly or were involved in the early trials of IPT [Reference Klerman, Dimascio, Weissman, Prusoff and Paykel10, Reference Weissman, Prusoff, Dimascio, Neu, Goklaney and Klerman11] or the NIMH Treatment of Depression Collaborative Study [Reference Elkin, Shea, Watkins, Imber, Sotsky and Collins12], were active in developing and testing the validity of adaptations of IPT. Academic hubs where IPT was taught to psychiatric residents and psychology interns were concentrated geographically to large cities in the northeast United States, most specially New York and Pittsburgh and were often siloed in medical centres where clinical research was conducted. While training in IPT existed, it often occurred as part of clinical research and involved postdoctoral fellows who were at early career stages of launching clinical research careers as well [Reference Weissman6]. The second generation of IPT developers, most notably Drs John Markowitz and Laura Mufson, two of Klerman’s last trainees, were instrumental in extending the evidence for the efficacy of IPT and related adaptations in IPT for individuals with HIV and post-traumatic stress disorders (PTSD) and depressed adolescents [Reference Mufson, Pollack Dorta, Moreau and Weissman40, Reference Markowitz, Petkova, Neria, Van Meter, Zhao and Hembree43, Reference Markowitz, Kocsis, Fishman, Spielman, Jacobsberg and Frances44]. Markowitz and Mufson’s advocacy and expertise as IPT trainers and supervisors highlighted and expanded the place of IPT in the evidence base for psychological treatment of mental disorders. However, most second generation IPT researchers were not exclusively training and supervising IPT therapists and did not have access to large cohorts of graduate students who were poised to enter clinical practice and teaching careers. Aaron Beck, in addition to being ‘the father of cognitive therapy’ and a pioneer in the field of evidence-based psychological treatments for depression and anxiety, founded a non-profit organisation, the Beck Institute in Philadelphia, Pennsylvania in 1994 with his daughter, Dr Judith Beck, a clinical psychologist. In a unique way, Beck crossed the aisle between psychiatry and psychology and influenced both fields as an insider and was more widely able to disseminate CBT through clinical psychology training programmes. Unlike the Beck Institute and other CBT training organisations, IPT did not develop free-standing, fee-for-service training institutes that provided post-graduate training and certification for mental health professionals to hone their skills and disseminate this modality of psychological therapy. In many ways, IPT has not gained the same degree of traction in clinical psychology training programmes in the United States, despite a cadre of seasoned clinical trainers and clinical researchers located in university-based hospitals and medical schools. However, it has experienced a great deal of success with implementation and dissemination efforts internationally [Reference Weissman and Mootz16], especially with the strong endorsement of the WHO and their inclusion of IPT in their mhGAP programme, recommendation of IPT as a possible first-line treatment for depression, and their publication of a manual for Group Interpersonal Therapy (IPT) For Depression [26].

Another factor that has contributed to the status of IPT as an evidence-based treatment for depression has been shifts in research funding priorities and the increased focus on identifying neural circuitry and response to psychological treatment in the United States [Reference Markowitz and Friedman45]. After the 2007 economic downturn left the NIMH with stinging budgetary cuts, funding opportunities available for large-scale clinical trials for psychological therapy were significantly reduced [Reference Torrey, Simmons, Hancq and Snook46]. Many expressed the idea that the evidence for the efficacy of interventions such as CBT and IPT were established and that research should now focus on disseminating treatment to community providers and assisting in implementing programmes of evidence-based treatments for depression in clinical settings outside of specialised medical centres and university-affiliated outpatient clinics. This movement to community settings and primary care presented an opportunity for IPT to move into broader systems of care but taxed the efforts of a relatively smaller cadre of clinical researchers without established pathways for providing outpatient mental health services in community venues. Still, one hypothesised barrier to the progression of IPT as a widely established evidence-based intervention for depression had to do with its overlap with neuroscience and NIMH’s roadmap for identifying neural mechanisms of treatment efficacy. In many ways the purported interpersonal mechanisms for producing symptom reduction when conducting IPT with adults and youths were less aligned with domains and constructs outlined in the new Research Domain Criteria (RDoC) as compared with the cognitive mechanisms postulated to underlie CBT [Reference Insel, Cuthbert, Garvey, Heinssen, Pine and Quinn47]. Although clinical trials of IPT were conducted during this period, few if any received funding associated with large scale studies of CBT that incorporated neuroimaging designs. The COVID-19 pandemic laid bare the dire consequences of investing in basic science and neuroscience at the expense of improving psychological treatments, psychiatric services and dissemination and implementation of innovative models of direct psychological care. It is not surprising that this approach has been reviewed with regret, even by some of its primary architects [Reference Barry48, Reference Torrey and Dailey49]. At present, the research funding for the sciences and mental health services in the United States continues to be uncertain despite the increasing need for evidence-based treatments. However, international implementation of IPT and large clinical trials in LMIC such as Mozambique [Reference Wainberg, Gouveia, Stockton, Feliciano, Suleman and Mootz50] as well as the digital translations [Reference Wainberg, Gouveia and McKinnon51] assure the continued dissemination of IPT.

Despite these setbacks, the IPT community has continued to thrive, expanding its evidence base, effective training and dissemination strategies and relevance to contemporary challenges for increasing access to mental health around the world. In 2002, the ISIPT was established with the mission and vision to advance the ‘broad application of IPT by therapists worldwide as one of the valuable means for alleviating human suffering due to mental disorders’ (https://interpersonalpsychotherapy.org). In service to this mission, ISIPT has centralised and operationalised criteria for certifying IPT therapists, supervisors and trainers, as well as offering annual application periods when new certifications across levels of experience are reviewed and approved. To date, ISIPT has hosted 11 biennial conferences, alternating locations between North America and Europe, bringing together therapists, clinical educators and researchers to share new directions, insights and findings related to applying IPT with different clinical populations, in different treatment contexts and in different cultural environments. IPT is consistently included in the US Preventative Task Force Recommendations for perinatal depression and the Substance Abuse and Mental Health Services Administration (SAMHSA.gov) recommendations for evidence-based psychological interventions for adolescent depression. The WHO recommends IPT as a first-line treatment for depression and it is consistently listed in the national consensus guidelines in the United Kingdom and Canada. There has been significant interest in IPT as a time-limited and effective modality of psychological treatment that can be disseminated with fidelity in LMIC and in the field of global mental health. These accomplishments are largely attributable to Weissman herself, who has always been a primary driving force behind growing and documenting the evidence base for IPT. In addition to her multiple programmes of epidemiological research on depression and inter-generational transmission of disorder in families, Weissman authored or co-authored a series of books for therapists and mental health professionals on IPT, its clinical adaptations and updated research in the last 20 years [Reference Weissman, Markowitz and Klerman14, Reference Weissman, Markowitz and Klerman15, Reference Weissman and Weissman52–Reference Markowitz and Weissman54]. Her most recent published book, entitled Interpersonal Psychotherapy: A Global Reach [Reference Weissman and Mootz16], contains summaries of clinical implementation and research on disseminating IPT in 31 different countries. Through continued efforts such as these, Weissman assured that IPT remains firmly ensconced as an evidence-based psychological intervention for depression and has evolved into thriving adaptations that engage new generations of researchers and therapists. IPT continues to address the changing needs and challenges of providing quality mental health care to diverse populations across the world.

The Legacy and Future of IPT

When asked what Dr Klerman would think of his academic legacy being so closely connected to IPT, Dr Weissman laughed and replied, ‘He would definitely be surprised and pleased’. This is a testament to Dr Klerman’s remarkable career trajectory given his first-generation status – first generation American citizen on his father’s side, first generation college-student, first generation medical student and MD – and how he pioneered significant changes in psychiatry and psychological science as part of the first generation of researchers conducting randomised clinical trials for pharmacology and psychotherapy and the first generation of psychiatric treatment providers developing manualised treatments and establishing empirically supported psychological therapies for depression. Dr Klerman also embodied qualities that made his research grounded in real-world applications: he thrived at elite institutions such as Harvard, Yale and Cornell, and was the head of the Alcohol, Drug Abuse & Mental Health Administration (ADMHA), but always worked with clients and students and had a keen eye on social determinants of mental health and the role of life events in the onset of depression. We would be remiss in not highlighting how Dr Weissman was an equally ground-breaking contributor to this paradigm shift in studying psychotherapy and the birth of evidence-based psychological intervention – she was the first female tenured professor in the Department of Psychiatry at Yale University. It is no wonder that these pioneers in our field were both kindred spirits as well as academic collaborators.

Dr Klerman had a life-long passion for learning, a characteristic that undoubtably contributed to his expertise and considerable accomplishments. He was well-read and loved the process of debating ideas. Open minded and never doctrinaire, Klerman challenged himself to understand all sides of an issue, sometimes actively taking up and arguing an opposite perspective for the sake of academic exercise. His premature death was a huge loss to the scientific community and to the next generation of IPT therapists and researchers. We remember him and are grateful for his shared vision with Weissman that has taken IPT from a ‘high contact’ placeholder for supportive psychological therapy to a real intervention that has endured as an efficacious treatment for depression and related emotional distress from universal interpersonal problems that are a part of the human condition.

Concluding Remarks

Understanding the history of IPT and how its development reflected the needs of a socio-political context in history, the state of the psychiatric science and the interpersonal community of individuals eager to improve psychological treatment for those suffering with depression orients us towards identifying future directions for IPT. The aftermath of the COVID-19 pandemic has continued to increase social isolation and disrupt interpersonal routines that form the structure of daily living for most individuals worldwide. The residual mental health crisis from this global pandemic will necessitate the need for increased providers trained in evidence-based interventions for adjustment disorders, depression and anxiety. IPT will certainly have a place at that table, as a treatment that can address individuals’ symptoms in the context of these social and historical transitions. The fact that IPT has been a leader in global mental health movement consolidates support for the future of IPT as a treatment that can be disseminated widely and with good results. The integration of telehealth delivery of mental health services, necessitated by the pandemic, has also presented new opportunities for examining the implementation and delivery of IPT virtually.

The state of the science of evidence-based interventions for depression is also changing in a way that maintains IPT’s role as a significant contributor to the next generation of psychological therapies. The push towards identifying and targeting transdiagnostic factors in treatment provides an opportunity to highlight the efficacy of IPT in reducing depressive and anxiety symptoms. The focus on trauma-informed and culturally sensitive care facilitates the employment of IPT techniques that allow us to understand an individual’s current functioning in relation to their social relationships and history of establishing social relationships, which are negatively affected by trauma. The increased focus on early interventions for psychological disorders expands the adaptations of IPT for children and adolescents. The adaptation of briefer forms of IPT that can be used with a task-shifting model of delivery are continuing to be developed by the Columbia University group and led by Dr Milton Wainberg for use in Africa and other LMIC as a part of regular care [Reference Oquendo, Duarte, Gouveia, Mari, Mello and Audet55]. Similarly, the use of neuroimaging methods will also provide additional areas of identifying neural changes that co-occur with changes in improving interpersonal relationships and reducing stressors related to loss, role disputes and role transitions in individuals undergoing IPT. These methodological advances in the study of psychiatric disorders present new directions for examining the effects of IPT on adults and youths. The upcoming chapters will address these and other issues that are at the forefront of the next generation of research, training and dissemination of IPT. Indeed, Dr Klerman would have unhesitatingly welcomed the challenge to incorporate new strategies for studying the science of psychiatric disorders and the effects of IPT.

The future of IPT retains a personal lens, in that it continues to capture the imagination of providing psychological therapy that focuses on key aspects of human experience, our relationships and significant events, such as loss, conflict and transitions, that change us and affect these relationships. And, in this way, the history of IPT continues to shape its future and contributes to its longevity and success as an evidence-based psychological treatment.