Executive functioning deficits among adults with Bipolar Disorder (types I and II): A systematic review and meta-analysis

BACKGROUND

Executive functioning (EF) deficits contribute to a significant proportion of the burden of disease associated with bipolar disorder (BD). Yet, there is still debate in the literature regarding the exact profile of executive functioning in BD. The purpose of the present project was to assess whether EF deficits exist among adults suffering BD, and whether these deficits (if apparent) differ by BD subtype.

METHODS

A systematic search identified relevant literature. Randomised controlled trials that used neuropsychological assessment to investigate EF among adults 16-65 years) with a remitted DSM diagnosis of BD (type I or II) were included. Studies were published between 1994 and 2015. A systematic review and meta-analysis were undertaken. For individual studies, standardised mean differences (Cohen's d) and 95% confidence intervals were calculated and represented in forest plots to illustrate differences in executive performance between groups. Summary effects were produced and tests of heterogeneity employed to assess the dispersion and generalisability of results.

RESULTS

Thirty-six studies met criteria for inclusion. Six domains of EF were identified: Set-shifting (SS), inhibition (INH), planning (PLA), verbal fluency (VF), working memory (WM), and attention (ATT). BD1s performed worse than HCs in all domains. BD2s demonstrated impairment in VF, WM, SS, and ATT. The results were mixed for comparisons between BD1s and BD2s, but revealed that BD2s can experience similar (or sometimes greater) EF impairment.

LIMITATIONS

Only a limited number of studies that included BD2 samples were available for inclusion in the current study. Subgroup analysis to elucidate potential moderators of within-study variance was not undertaken.

CONCLUSION

This is the first systematic review and meta-analysis to have compared the EF of remitted BD1s, BD2s, and HCs. The results provided useful insight into the EF profile of patients with BD, and offered commentary as to some of the contradictory results reported in the literature. A standardised methodological protocol for assessment of EF in BD was proposed. The information in this review could enhance our understanding of EF impairment inherent in BD, and the methods and efficacy with which clinicians assess and treat this population.

The utility of IFS (INECO Frontal Screening) for the detection of executive dysfunction in adults with bipolar disorder and ADHD

Bipolar disorder (BD) and attention deficit hyperactivity disorder (ADHD) in adults share clinical symptoms. Both disorders present with executive functioning impairment. The detection of executive dysfunction usually requires the administration of an extensive neuropsychological battery. The Institute of Cognitive Neurology (INECO) Frontal Screening (IFS) is an efficient tool, which has been demonstrated to be useful for the detection of executive deficits in other diseases involving the prefrontal cortex. This study assessed the usefulness of the IFS in detecting the executive dysfunction of BD and ADHD adults, by means of a receiver-operating characteristic curve analysis and a multigroup discriminant function analysis. Twenty-four BD, 25 ADHD patients and 25 controls were assessed with a battery that included the IFS and other measures of executive functioning. Our results showed that both patient groups performed significantly lower than controls on the IFS total score. Using a 27.5 point cut-off score, the IFS showed good sensitivity and acceptable specificity to detect executive impairments in BD and ADHD patients. The IFS discriminated between controls and each patient group more reliably than other executive functions measures. Our results suggest that this tool could be a useful instrument to assess executive functions in BD and ADHD patients.