Psychiatric Comorbidities in Adult Attention Deficit Hyperactivity Disorder: Sex-Based Patterns of Internalizing and Externalizing Disorders in a Clinical Sample

Objective: Attention-deficit/hyperactivity disorder (ADHD) affects 2.5% of adults, with high comorbidity rates (70–80%) and sex-based patterns. This study aimed to examine the prevalence of psychiatric comorbidities in adult patients with ADHD, with a focus on internalizing and externalizing disorders across sexes. Method: This cross-sectional observational study examined data from 70 adult patients (aged 18–60 years) diagnosed with ADHD who sought treatment at Koru Ankara Hospital between April 2022 and September 2023. Psychiatric comorbidities were retrospectively identified from electronic patient records. Comorbidities were categorized as externalizing (alcohol/substance use disorders, impulse control disorders, and personality disorders) or internalizing (anxiety disorders, depressive disorders, eating disorders, and obsessive–compulsive and related disorders), and comorbidity patterns between sexes were compared. Results: At least one psychiatric comorbidity was found in 71.4% of the patients (69% female, 75% male). The most common comorbidities were anxiety (34.3%) and mood disorders (20%), including major depressive disorder (15.4%), bipolar disorder (2.9%), and dysthymia (1.4%). Men had significantly higher rates of alcohol/substance use disorders and externalizing disorders, whereas internalizing disorders were not significantly different between the sexes. Patients with both internalizing and externalizing disorders were predominantly male. Conclusion: Psychiatric comorbidities are prevalent in adults with ADHD. While internalizing disorders showed no sex differences, externalizing disorders were significantly more common in men, highlighting the need for sex-specific comorbidity screening in clinical practice. Future studies should use larger, longitudinal, and multicenter designs to better understand developmental pathways and support personalized treatment strategies.