Cognitive impairment in bipolar disorder and related populations

It is well established that cognitive impairment exists in patients with bipolar disorder (BD), with these deficits enduring in remitted or euthymic states. BD patients often display impairments in the domains of attention, memory and executive functions Reference Harvey, Wingo, Burdick and Baldessarini(1). Such impairments contribute to poor functional outcomes, particularly in areas related to independent living, social relationships and occupational functioning Reference Harvey, Wingo, Burdick and Baldessarini(1,Reference Wingo, Harvey and Baldessarini2).

Functional outcomes are also defined in terms of regaining premorbid levels of psychosocial and occupational status, and the ability to perform daily life skills. In a BD population, recent figures showed that only 19–23% of adults with bipolar disorder type I (BD-I) were married, 19–58% were not living independently, 57–65% were unemployed, and up to 80% displayed some degree of vocational disability Reference Huxley and Baldessarini(3). Indeed, functional outcomes are granted equal weighting to symptomatic recovery when evaluating treatment outcomes for BD; however, studies on the effects of interventions on functional outcomes for BD patients are rare.

Cognitive impairment in BD shares some similarities with that seen in schizophrenia (SZ) and acquired brain injury (ABI), especially traumatic brain injury (TBI). The main divergence between SZ and BD is in the severity of impairment Reference Yatham, Torres and Malhi(4). Considering these points, interventions created for use in the SZ and TBI populations may have some utility for use in a BD population. In particular, one relatively new area of research is based on the success of interventions utilising a cognitive remediation (CR) paradigm, which can serve as a model for BD.

Aims and methods of cognitive remediation in schizophrenia and TBI

Research has focused on outcomes associated with the domains of independent living, occupational functioning, social competence and medication management. As in BD, these functional outcomes are associated with specific cognitive deficits; therefore, CR programmes aim to improve cognition and facilitate functional outcomes for patients.

Generally, the approaches to improving cognitive functioning are exemplified as either ‘cognitive enhancing’ or ‘compensatory’Reference Kern, Glynn, Horan and Marder(5). Cognitive-enhancing programmes focus on improving impaired cognitive functions Reference Kern, Glynn, Horan and Marder(5,Reference Medalia and Choi6), whilst compensatory programmes tend to bypass treating the cognitive deficits per se, and instead, recruit external aids or structured processes to compensate for cognitive deficits. Methods of cognitive training are generally categorised as being computer- or clinician-assisted Reference Harvey, Wingo, Burdick and Baldessarini(1,Reference Medalia and Choi6).

Cognitive remediation in schizophrenia

Fisher et al. Reference Fisher, Holland, Merzenich and Vinogradov(7) administered a neuroplasticity-focused computer-based cognitive-enhancing CR method for improving verbal memory in SZ patients. The SZ patients receiving this intervention showed increased global cognition, verbal learning and verbal working memory compared to the control group. These gains were maintained for areas of verbal learning and memory in a sample of participants who were measured at 6-month follow-up Reference Fisher, Holland, Subramaniam and Vinogradov(8). Another computer-based CR programme was utilised in a psychiatric population consisting of SZ, schizoaffective and bipolar patients Reference Lindenmayer, Mcgurk and Mueser(9). The intervention for this study engaged patients in cognitive exercises for attention, concentration, learning and memory and executive functions, and they participated in weekly group discussions to assist transfer of cognitive skills to daily life. Compared to those in the control group, participants who completed the CR programme displayed a trend towards better outcomes in vocational functioning by working more hours and earning higher wages, and they also showed better cognitive performance in the domains of attention, psychomotor speed and learning.

Velligan et al. Reference Velligan, Diamond and Maples(10) utilised Cognitive Adaptation Training (CAT) as a compensatory CR approach for functional behaviours in an SZ population versus a generic programme of environmental support, and treatment as usual (TAU). Examples of environmental support in this study included medication adherence, grooming and hygiene, leisure skills and orientation and scheduling. The CAT programme consisted of a manual of environmental supports specifically tailored to each patient, and consisted of more frequent clinician contact, more intense therapeutic contact, addressed all domains of adaptive functioning, and was carried out in the patient's home Reference Velligan, Mueller and Wang(11). The authors found that CAT improved functional outcome in SZ patients. When treatment frequency was reduced, the functional gains for the CAT group were reduced to that of the generic supportive treatment group, although the functional outcomes were significantly better than the TAU group. Higher intensity of treatment therefore produced the greatest outcomes for functioning in this study.

A meta-analysis conducted by McGurk et al. Reference Mcgurk, Twamley, Sitzer, Mchugo and Mueser(12) established that CR programmes for SZ patients tend to be associated with significant, albeit modest, improvement in cognitive performance and functional outcomes, in addition to general symptomatic improvement. These improvements incorporate attention, verbal learning and memory, problem solving and processing speed. Further, sizes with the biggest effect occurred in those studies that incorporated CR techniques with psychosocial rehabilitation techniques. Evidently, the best interventions focus not only on treating cognitive dysfunction, but also on deficits in social skills, vocational training and in offering psychological support.

CR programmes in TBI

BD patients and those with mild to moderate TBI share a similar cognitive deficit profile in the areas of memory, executive function and processing speed, and may have comparable levels of deficit, although there is a paucity of literature on the association between BD and TBI. Cicerone Reference Cicerone(13) found beneficial effects on attention after a compensatory CR programme that consisted of tasks including ‘n-back’, random generation and dual-task processes in patients with mild TBI. Tiersky et al. Reference Tiersky, Anselmi and Johnston(14) found that mild and moderate TBI patients administered a compensatory CR programme combined with cognitive behavioural therapy (CBT) experienced improvement in anxiety and depression scores, and improved cognitive performance in a divided auditory attention task. This indicates that CR interventions combining CR and CBT have some utility in reducing psychological distress and improve cognitive functioning.

Applying interventions for schizophrenia and TBI to BD

CR interventions have had a degree of success in SZ and TBI populations, improving cognitive performance and functional outcomes. These interventions can serve as a model for remediation in a BD population, as all these disorders share similar profiles of cognitive impairment.

One study measured the effects of a clinician- and computer-administered neuropsychological educational approach to remediation (NEAR) CR programme on psychiatric patients including a sample of SZ and BD patients Reference Choi and Medalia(15). This approach focuses on CR as a top–down strategy-based method based on basic educational principles that have been shown to facilitate learning Reference Kern, Glynn, Horan and Marder(5). The authors found that patients receiving the intervention displayed improved attention and employment-related behaviours such as better work quality, work habits and cooperation, which highlights the importance of cognitive training as an engaging format so that patients are naturally motivated to complete the programme.

To date there has been only one CR pilot study applied solely to BD patients, adapted from SZ remediation research. Deckersbach et al. Reference Deckersbach, Nierenberg and Kessler(16) measured functional outcomes for BD patients after a CR intervention incorporating a clinician-administered CBT component to address residual depressive symptoms, and a compensatory CR strategy for cognitive functions including attention, memory, planning and organisation abilities. Functional outcomes were primarily measured using the World Health Organisation (WHO) Health Performance Questionnaire Reference Kessler, Barber and Beck(17), and other measures to assess overall psychosocial functioning in the areas of work, relationships, recreation and overall satisfaction. The authors found that after their intervention, patients experienced lower residual depressive symptoms, and improved occupational and general psychosocial functioning levels. In particular, improvements in executive functioning were associated with better occupational functioning.

This pilot study in BD identified that interventions for BD patients may need to focus on mood symptoms in addition to treating cognitive deficits, as mood symptoms may also affect functional outcomes.

How can clinicians enhance functional improvement in BD?

Goal setting with BD patients to determine their desired and realistic levels of functioning is necessary, whilst also considering the strengths and weaknesses of the person. Implementing an intervention and measuring outcomes in BD patients need to be guided by three approaches. First, the clinician needs to consider the essential measurement of mood, as this can affect the patients' ability to be motivated to engage in treatment. Deckersbach et al. Reference Deckersbach, Nierenberg and Kessler(16) found that BD patients with a history of anxiety tended to have more anxious reactions to occupational situations, which interfered with functioning. Similarly, depressed mood can interfere with engagement in psychological treatment programmes, primarily because of the lack of motivation and drive Reference Harvey, Wingo, Burdick and Baldessarini(1). Strategies to promote engagement such as activity planning could therefore be incorporated in CR treatment programmes for BD. Second, functional capacity and performance should be measured using objective functional assessment, as it is likely that subjective appraisal could lead to bias, and mood state would cloud estimates of current functioning. Third, cognitive functions should be measured across various clinical states in BD using a standard cognitive test battery. Recently, a preliminary battery of cognitive tests has been created to measure and understand the nature of cognitive deficits in BD Reference Yatham, Torres and Malhi(4). The authors identified that the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) Consensus Cognitive Battery (MCCB), created for use in SZ patients, offers a model for creating a similar battery for BD, with the addition of tasks assessing more complex verbal learning and executive functions Reference Yatham, Torres and Malhi(4).

Conclusion

Research into CR interventions for clinical populations who are cognitively compromised has paved the way for future research in BD. The initiation of such interventions can be supplemented by measuring cognition across different mood states using a standard cognitive battery of tests, and treatment can subsequently focus on addressing mood as well as cognitive compromise. Interventions can utilise a cognitive enhancing or compensatory focus using clinician- and computer-based administration methods. The paucity of literature on CR interventions in BD patients emphasises a need to develop this area further.