Objective: This study, with a case-control design, investigates the impact of attention-deficit/hyperactivity disorder (ADHD) comorbidity on the phenomenology and treatment outcomes in a clinical sample of pediatric obsessive-compulsive disorder (OCD). Methods: The data were derived from an evaluation of the sociodemographic and clinical characteristics of 364 children with OCD who were regularly followed up over a 4-year period. Between-group analyses of psychiatric scales were used to compare patients with ADHD comorbidity (n = 144, 39.5%) with their ADHD-free opponents. The clinical course and treatment outcomes of each patient were evaluated based on 4-year clinical follow-up data. Results: Substantial clinical variations in pediatric OCD caused by ADHD comorbidity were identified, including a male preponderance, higher rates of concurrent conduct problems, tic disorders, and learning disabilities, as well as prolonged symptom and treatment durations accompanied by poor response to first-line treatments and higher rates of treatment resistance. Contrary to previous findings, ADHD comorbidity had no impact on the age of OCD onset, and the severity of OCD symptoms was lower in ADHD. With ADHD comorbidity, the OCD symptom course tended to be chronically stable, which may have resulted in complaints persisting into adulthood. In ADHD-free patients, contamination, doubt, religious, somatic obsessions, and cleaning were all more common than in those with ADHD. There was a positive correlation between compulsion scores and the severity of ADHD symptoms, which may be related to increased compulsive coping in ADHD. Impulsivity or compulsivity dominance in the symptom presentation of OCD-ADHD comorbidity may determine phenomenological distinctions such as whether concurrent traits are more prone to tics, conduct problems, or internalizing problems. The primordial associations for clinical characteristics, which were independently associated with ADHD comorbidity, were adjusted using multivariate logistic regression analysis. Clinical variables such as being male, absence of cleaning compulsion, the existence of concurrent conduct problems, tic disorders, and dyslexia, as well as longer treatment duration and poorer treatment response, were all independent predictors of ADHD comorbidity. With an 80.8% accurate classification and relatively fine goodness-of-fit model, the regression model consisting of those predictors had good predictiveness for ADHD comorbidity (R2 = 0.543). Conclusions: The close association between pediatric OCD, ADHD, and tic disorders can be defined as a specific subtype of pediatric OCD, characterized by more conduct problems, a chronically stable course of OCD symptoms, and poorer treatment outcomes. Correlational analyses in a longitudinal design and the inclusion of an impulsivity scale would be beneficial for further research to interpret the impulsivity-related correlates in the findings on tic and conduct problems.
Keywords: ADHD comorbidity; child psychiatry; pediatric OCD; phenomenology; treatment outcomes.