Attention-Deficit/Hyperactivity Disorder Symptoms in Adults With Obsessive-Compulsive Disorder: Associations With Symptom Dimensions

Objective Obsessive-compulsive disorder (OCD) and attention-deficit/hyperactivity disorder (ADHD) share overlapping cognitive and neurobiological features, yet data on ADHD symptomatology in adults with OCD remain limited. This study aimed to examine the association between ADHD symptom severity and OCD symptom dimensions in an adult OCD sample.Methods Ninety-four adults diagnosed with OCD according to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition criteria were recruited from an outpatient psychiatry clinic. OCD severity and symptom dimensions were assessed using the Yale–Brown Obsessive Compulsive Scale (Y-BOCS). ADHD symptom severity was evaluated with the Adult ADHD Self-Report Scale (ASRS), including inattention and hyperactivity subscales. Correlation and multiple linear regression analyses were conducted to examine relationships between ADHD symptom dimensions and OCD severity.Results Higher ASRS total scores were significantly associated with greater Y-BOCS total scores (r=0.40, p<0.001). Inattention symptoms were more strongly associated with total obsession (β=0.37, p=0.008) and total compulsion scores (β=0.41, p=0.003) than hyperactivity symptoms. Regression models indicated that inattention, but not hyperactivity, independently predicted OCD symptom severity. ADHD symptom severity was negatively associated with global improvement scores.Conclusion ADHD symptoms, particularly inattention, were associated with greater OCD symptom severity within this OCD sample. These findings suggest that ADHD symptoms, particularly inattention, may be relevant in understanding variability in OCD severity within clinical samples. Further studies are needed to clarify underlying mechanisms and clinical implications.