‘Persecutory delusions’, edited by Daniel Freeman, Richard Bentall and Philippa Garety is perhaps the most comprehensive collection of papers on the topic of paranoia and persecutory delusions. The editors, all acknowledged experts in the field, have long made an argument for the use of the single symptom approach in research to better understand the processes associated with delusions, and this book brings together various aspects of research on delusions. The opening chapter, by Peter Chadwick gives a personal account of his experience of psychosis and the process of recovery. Chadwick's writing is erudite and his perspective is unique. I thought it was a great way to start the book. It is a story of hope that I've shown to clients in therapy, and one they very much liked. The rest of the book is divided into sections covering assessment and epidemiology, psychological processes associated with delusions, biological processes, and treatments – with a final section of CBT case studies – again including a first-person account of the process of therapeutic change (Murphy and Smith).
Daniel Freeman's chapter examines the complexities in the definition and assessment of paranoia and persecutory delusions and highlights a number of different measures – from ‘general’ measures like the PANSS to other measures developed to examine specific aspects of paranoia – such as the PSYRATS, or scales of ‘deservedness’, cause and safety behaviours. Freeman et al.'s other chapter deconstructs different factors associated with delusions, and how the use of different experimental designs might allow us to disentangle these processes. They also examine the role of anxiety and provide an overview of the psychological and cognitive processes thought to be associated with anxiety.
Rutten et al. present data from NEMESIS – the Dutch longitudinal epidemiological study, which examined the premorbid factors associated with paranoia as well as pathways in the course and consequence of psychiatric disorders, highlighting the role of moderating factors such as victimization, perceived discrimination, trauma, and mediators such as neuroticism and stress reactivity – some of which Chadwick also alludes to in his chapter. Harrow et al. also present longitudinal data, tracking prognosis and outcomes for patients with paranoia over a 20-year follow-up. Jayne Taylor's chapter summarizes the risk factors associated with violence in schizophrenia, including, importantly, the methodological weaknesses in the studies to date. Alistair Munro's chapter on delusional disorder surveys the brief literature on the phenomenology of the illness and points out that our understanding of the disorder is limited and made worse by common beliefs professionals hold – including that they are impossible to treat. He suggests that 50% of patients with delusional disorder respond well to medication and others respond well to psychotherapy. He also makes a compelling case for why we should study delusional disorder – suggesting that the switch between what he refers to as the ‘delusional’ and ‘normal’ modes of functioning (which can be seen in many patients) might allow for some interesting within-subject comparisons. He ends with some helpful tips on how to find and recruit such patients.
Cognitive factors associated with delusions have been extensively studied, and many of these processes are examined in great detail here – including anxiety (Freeman et al.), self-esteem and its link to attribution biases (Bentall et al.), theory-of-mind deficits (Corcoran & Kaiser), and social cognition deficits (Combs & Penn). Combs and Penn also integrate these findings into their training programme for social cognition (SCIT). Langdon et al. describe their two-factor theory and the neuropsychological approach which they have applied to monothematic delusions. They suggest that this approach might also be applied to persecutory delusions, identifying deficits such as hallucinations, referential ideation and attentional biases as the potential ‘factor 1’ in their two-factor model.
The section on biological process and pharmacological treatments highlighted to me that there is little known here that is specific to paranoia and persecutory delusions. Thus most of the chapters talk about positive symptoms or psychosis as a whole, and indicate putative links to paranoia. Marc Laruelle covers the evidence of dopaminergic abnormalities in schizophrenia and its links to other neurotransmitter systems (GABA/NMDA). Similarly Henquet et al. describe both the research findings and possible causal mechanisms through which cannabis might cause psychosis in vulnerable individuals. Broome et al. cover a disperse body of literature on imaging and psychosis, touching on data from PET studies, structural imaging and fMRI. They highlight the difficulties of trying to ‘image a delusion’ as these are not discrete states, and a number of assumptions are involved in such a process. They examine the neural correlates of some of the cognitive biases associated with delusions and structural and functional changes associated with the transition to psychosis.
The final two sections, on treatments, touch upon pharmacology (Bebbington et al.), but focus largely on psychosocial interventions including family interventions (Onwumere et al.) and cognitive behavioural therapy (CBT). These chapters include reviews of the existing research literature on treatment efficacy (Garety et al.) as well as detailed case studies and intervention strategies (Parker et al.; Murphy & Smith; Kingdon et al.; Chadwick & Trower). I found these chapters particularly fascinating as they highlight the commonalities in treatment approaches as well the differences, which suggest the need for individually tailored treatments, and might account for some of the heterogeneity in outcomes seen in research studies. Going forward it seems to me that we need to decide whether we need to further modify treatments to increase efficacy given this heterogeneity of outcomes, or resign ourselves to the idea that CBT may only help some of our patients, and try to find ways to identify who those might be. I also wonder whether data from novel treatment approaches like meta-cognitive training (Moritz & Woodward), which attempt to correct the cognitive biases associated with delusions might specifically help patients with paranoia, and whether social initiatives such as anti-bullying programmes, which may help reduce childhood trauma might act as ‘early treatment approaches’ eventually leading to reduced prevalence of paranoia and psychosis.
Overall, I found the chapters uniformly well written and informative and a good snapshot of the current state of literature on the topic, and I'd highly recommend the book to anyone with research or clinical interest on the topic of paranoia and persecutory delusions.
