Comorbid personality disorders (PDs) are discussed as risk factors for a negative treatment outcome in obsessive–compulsive disorder (OCD). However, studies published so far have produced conflicting results. The present study examined whether PDs affect treatment outcome in patients with OCD.

The treatment sample consisted of 55 patients with OCD who were consecutively referred to a Behaviour Therapy Unit for an in-patient or day-clinic treatment. Treatment consisted of an individualised and multimodal cognitive behaviour therapy (CBT, with or without antidepressive medication). Measurements were taken prior and after treatment and 6-month after admission.

A large percentage of patients benefited from treatment irrespective of the presence of a PD and were able to maintain their improvement at follow-up. Duration of treatment was not prolonged in OCD patients with concomitant Axis II disorders. However, some specific personality traits (schizotypal, passive–aggressive) were baseline determinants for later treatment failure at trend level.

Results are encouraging for therapists working with patients co-diagnosed with Axis II disorders since these patients are not necessarily non-responders. The results stress the importance of a specifically tailored treatment approach based on an individual case formulation in OCD patients with complex symptomatology and comorbid Axis II disorders.