Neurocognitive functions and social cognition in bipolar disorder, attention deficit hyperactivity disorder, and comorbid bipolar disorder–attention deficit hyperactivity disorder

Introduction

Bipolar disorder (BD) and attention deficit hyperactivity disorder (ADHD) frequently co-occur, and this comorbidity (BD+ADHD) is associated with greater clinical complexity, overlapping symptoms, and poorer functioning. Despite growing interest in this diagnostic overlap, the neurocognitive and social cognitive profile of individuals with BD+ADHD remains unclear. While some studies suggest that BD+ADHD show cognitive performance comparable to BD [1,2,3] and lower than ADHD [1,3], others report more pronounced impairments across domains in comorbid case[4,5].

Aims

This study aimed to compare BD, ADHD, and BD+ADHD groups with each other and with healthy individuals (HC) in terms of neurocognitive functions, social cognition, and social functioning. The study hypotized that individuals diagnosed with BD, ADHD, and BD+ADHD, as well as HC, would display different profiles in cognitive functions, social cognition, and social functioning.

Methods

A total of 124 participants were included: 31 with BD, 33 with ADHD, 30 with BD+ADHD, and 30 HC recruited from the Ankara University Faculty of Medicine Department of Adult Psychiatry. Diagnoses were established using the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition and the Diagnostic Interview for Adult Attention Deficit/Hyperactivity Disorder. Depressive and manic symptoms were assessed with the Hamilton Depression Rating Scale (HAM-D) and Young Mania Rating Scale (YMRS) and individuals scoring above 8 on the HAM-D or above 7 on the YMRS were excluded. Participants completed the Adult Attention Deficit/Hyperactivity Disorder Self-Report Scale and Social Adaptation Self-Evaluation Scale. Cognitive assessment included the Verbal Memory Processes Test, Wechsler Adult Intelligence Scale Revised Similarities subtest, Stroop Test, and Trail Making Test A and B, Reading the Mind in the Eyes Test. The evaluated cognitive domains included verbal memory and learning, executive functions, inhibition control, premorbid intelligence, and social cognition/theory of mind. Distributional characteristics were assessed with the Shapiro–Wilk test, and group comparisons were performed using parametric or nonparametric tests as appropriate, with chi-square or Fisher exact tests for categorical variables. Analyses of covariance controlling for age, education, and premorbid intelligence were performed, and statistical significance was set at p<0.05.

Results

Groups differed significantly in age (χ²=27.472; p<0.001) and education (F=12.622; p=0.004), with lower educational attainment and older age in BD. Depressive symptoms were highest (χ²=9.563; p=0.023) and social functioning was lowest in BD+ADHD (x2= 19.505; p<0.001). After controlling for age, education, and premorbid intelligence, the only significant between-group differences were observed in inhibitory control and verbal memory. Both BD (p = 0.05) and BD+ADHD (p < 0.001) showed poorer inhibitory control than HC, whereas reduced verbal memory performance was observed only in the BD compared with HC (p = 0.04).

Conclusions

The attenuation of most cognitive differences after controlling for covariates suggests that processing speed, executive functions, and social cognition may be influenced more by sample characteristics than diagnostic category. Nevertheless, persistent impairments in inhibitory control and verbal memory in BD and BD+ADHD indicate residual cognitive vulnerability even during remission. The observed cognitive profile of patients support the clinical relevance of routine cognitive assessment and consideration of cognitive rehabilitation strategies in long-term management.

References

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