Comorbidities in OCD have been examined, discussed and classified from different perspectives. Historically, relationships with anxiety disorders have been strongly emphasised, demonstrated by OCD's placement among anxiety disorders. However, with many OCD presentations extending beyond anxious states (e.g., disgust, “not-right” as the core negative valence state), the DSM-5 (1) has evolved to categorise OCD outside of the anxiety disorders and along with select phenomenologically similar comorbidities [Obsessive-Compulsive Related Disorders (OCRDs)]. Correspondingly, tic disorders have been examined as phenotypic markers for a homogeneous subgrouping among heterogeneous presentations of OCD (10–12), and their lifetime presence is a DSM-5 OCD specifier. Recent reviews have examined the epidemiological, clinical and psychopathological relationships between certain personality disorders, specifically schizotypal personality disorder (9) and obsessive-compulsive personality disorder (13), and OCD, suggesting the relevance of systematic clinical assessments and a need for further clinical, neurobiological and genetic enquiry in this area. Very few studies have systematically examined medical/neurological comorbidities in OCD. Risk of metabolic syndrome in OCD rises perhaps with the use of atypical antipsychotics as augmenting agents, with one study documenting more than 20% prevalence, much higher than general population estimates (14).
