Working memory network alterations and associated symptoms in adults with ADHD and Bipolar Disorder

Attention-Deficit/Hyperactivity Disorder (ADHD) and Bipolar Disorder (BPD) co-occur frequently and represent a particularly morbid clinical form of both disorders, however underlying neural circuitry contributing to the comorbidity remain understudied. Our aim was to investigate functional brain circuitry during working memory in a group of participants who meet criteria for both disorders (ADHD + BPD), and to explore the relationship of symptoms of each disorder to brain function. We used fMRI to image brain activity in 18 male adults with both ADHD and BPD, and 18 healthy control participants matched one-to-one on age, sex, and handedness, while they performed a sequential letter N-back task. We investigated differences in activation between these groups, and also correlations of brain activity during the task to symptoms of ADHD and BPD independently. We found significant hypoactivity in the subjects with ADHD + BPD vs. controls across frontal and parietal regions, and further, found that BPD and ADHD symptoms related to activity in anatomically distinct regions that were respectively characterized by activation and suppression during task. We conclude that comorbid ADHD + BPD is associated with alterations across anterior and posterior nodes of the working memory network, and symptoms of each disorder are related to anatomically and functionally distinct brain regions.