Unravelling the comorbidity between OCD and ADHD

By Ilinca Mihailescu

Blanco-Vieira TSantos MFerrão YATorres AR3Miguel ECBloch MHLeckman JFdo Rosario MC (2019). The impact of attention deficit hyperactivity disorder in obsessive-compulsive disorder subjects. Depress Anxiety. [Epub ahead of print]. doi: 10.1002/da.22898. https://www.ncbi.nlm.nih.gov/pubmed/30990937


Recent findings suggest an association between attention deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD). Thus, we evaluated the clinical associated features of ADHD in a large sample of adult OCD patients.

A cross-sectional study including 955 adult patients with OCD from the Brazilian Research Consortium of Obsessive-Compulsive Spectrum Disorders (C-TOC). Clinical characteristics in adult OCD patients with and without comorbid ADHD were compared using Fisher’s exact test, t-tests or Mann-Whitney tests. Bivariate analyses were followed by logistic regression analysis to identify clinical characteristics independently associated with ADHD comorbidity.

The lifetime prevalence of ADHD in adult OCD patients was 13.7%. The current results indicate that OCD + ADHD patients were more severe, had an earlier onset of the obsessive-compulsive symptoms, a higher history of rheumatic fever, with higher frequencies of sensory phenomena and comorbidity with Tourette syndrome. They also had an increased risk for academic impairment and suicide attempts.

Adult OCD patients with ADHD present some specific clinical features and may represent a special subgroup of adult OCD. Future studies should focus on the development of interventions more tailored to the phenotype of this subgroup of patients.

Short comment
Although it is largely acknowledged that the concept of comorbidity in psychiatry is still a conundrum and that the explanatory models regarding the co-occurrence of different disorders are far from being completely understood, the association of two or more mental problems in the same patient are rather the rule than the exception. Since choosing a treatment plan or forecasting a prognosis is crucial, the proper assessment of these cases with multiple comorbidities is, therefore, essential, particularly for disorders such as ADHD, where the lifetime co-morbidity rate reaches 60–80% (Kooij 2019).

This new study stands out because it investigates the impact of ADHD in the largest sample of adult OCD patients assessed so far (955 patients), and because it analyses the effect of ADHD on the severity of specific OCD dimensions, the presence of sensory phenomena, academic performance and suicidality risk.

The results showed that the ADHD prevalence rate in OCD patients in this research was 13.7%, which is markedly higher than the one expected for adults in the general population. An earlier age of OCD onset was associated with ADHD comorbidity, and the OCD + ADHD group had a higher symptom severity in all DY‐BOCS dimensions (except for the contamination/cleaning), as well as higher DY‐BOCS impairment and total global scores (Blanco-Vieira 2019). As the authors stated, the group of patients having both disorders are more severely affected, which is particularly important in terms of outcome, emphasizing the role of screening and implementing effective treatment strategies.

Among other findings, this research showed that the OCD patients with an additional Tourette syndrome diagnosis had more than double the chances of having ADHD comorbidity, the OCD+ADHD group were more likely to report sensory phenomena and more patients with both disorders declared failed academic years in their lifetime (Blanco-Vieira 2019).

One other interesting aspect refers to the relationship between this comorbidity and suicidality. Suicide attempts among OCD + ADHD patients in this study were almost two times higher compared to OCD adults without ADHD (18% vs 9%), which comes in line with the reports of previous studies that found a 16% rate of suicide attempts in adults with ADHD (Balazs 2017).

Overall, the study published by Blanco‐Vieira T. and his colleagues has comprehensively described the clinical picture of OCD and ADHD comorbidity, which may consequently lead to a better understanding, assessment and quality of care of these patients.