Neurocognitive Functions in Bipolar Disorder in Relation to Comorbid ADHD

Bipolar disorder (BD) and attention deficit hyperactivity disorder (ADHD) often co-occur in adult population. Both conditions present various neurocognitive and behavioral problems. We aimed to examine neurocognitive functions in adult patients with comorbid BD and ADHD (BD+ADHD) in comparison to patients with only BD, only ADHD and healthy controls (HCs). An extensive cognitive battery which evaluates verbal learning and memory, visual memory, processing speed, attention, executive functions, working memory and verbal fluency, was used to assess neurocognitive functions respectively in adult (age 18-65 years) patients with BD (n=37), ADHD (n=43), BD+ADHD (n=20) in comparison to HCs (n=51). The Multivariate Analysis of Covariance models, where age, level of education and total BIS-11 scores were included as covariates, were used for comparing neurocognitive scores among groups. Both BD and BD+ADHD groups showed significantly poorer performance than HCs in processing speed, attention, executive functions, and verbal fluency domains. The BD group had additional significant deficits in executive functions, verbal learning and memory domains. There were no significant differences between BD and BD+ADHD groups with regards to verbal learning and memory, visual memory, processing speed, attention, executive functions, working memory and verbal fluency domains. Patients with only ADHD showed significantly poorer performance than HCs in verbal fluency domain. Our results show similarities in the neurocognitive functions of adults with BD and BD+ADHD across a wide range of cognitive domains. The findings point to the need for further exploration of diverging and converging neurodevelopmental trajectories of BD and ADHD.