Background
Obsessive-compulsive disorder (OCD) and psychotic disorders exhibit both biological and phenomenological overlap.[1] Furthermore, there might not be a clear distinction in OCD between delusions and obsessions as OCD patients describe varying degrees of overvalued ideas.[2] Studies also indicate that obsessions can transform into delusions,[3] and that OCD and symptoms of OCD can be associated with the development of psychotic disorder over time.[4] An increased prevalence of OCD in patients with first-episode psychosis has also been found.[5] Although this may seem to link OCD and psychotic symptoms, other studies show mixed evidence concerning this relation, leaving unanswered the question of whether psychotic and schizotypal symptoms are particularly associated with OCD, or whether they constitute symptoms that are just as prevalent in several other emotional disorders.
Some studies have explored psychotic symptoms in patients with OCD.[4,6–10] It has been argued that a symptom-based approach may be more favourable than a diagnostic approach due to questionable validity of diagnostic systems, substantial variation in symptomatology within categorical diagnosis and the ignoring of likely continua in the symptomatology between normal and pathological.[11] However, there is great variety in the reported occurrence of such symptoms, ranging from zero to fifty percent.[4]
There have been proposals of a distinct subtype of schizotypal OCD,[3,6,12] as OCD patients with schizotypal symptoms have poorer insight and lower functioning than OCD patients without such symptoms. However, there are discrepant findings. One study found that patients with depression, panic disorder, social phobia, post-traumatic stress disorder, or alcohol/substance dependency, had higher life-time prevalence of schizotypal personality disorder than patients with OCD.[7] A second study found that patients with OCD reported more symptoms of schizotypal disorder than patients with depression, but less so than patients with bipolar disorder or schizophrenia.[13] A third study found that OCD patients with schizotypal symptoms reported higher rates of comorbid major depression, post-traumatic stress disorder, substance use disorders, and greater general psychopathology.[14] They did not find any associations between schizotypal symptoms and OCD when controlling for differences in demographics and comorbidity.
To further complicate matters, a longitudinal study argued that sub-clinical levels of psychotic disorders are associated with development of anxiety, emotional and substance-related disorders.[15] Unlike the studies mentioned above, this study indicated that such an association was stronger between OCD and psychotic symptoms, than any of the other disorders. The proposed association between symptoms of OCD and psychotic and schizotypal symptoms may also be moderated by symptom severity[16] because low levels of schizotypal and OCD symptoms were distinct from each other, whereas among high scoring individuals the two symptom categories were associated. Thus, it remains uncertain if psychotic and schizotypal symptoms are linked to OCD.
The presence of psychotic and schizotypal symptoms may influence treatment outcome in OCD. Indeed, previous studies indicate that OCD patients with comorbid schizotypal disorder show poorer response to medical treatment for OCD.[3] Related research comes from studies on poor insight in OCD. OCD with poor insight has been described as egosyntonic symptoms that might extend to delusions and psychosis.[17] Most likely, insight falls on a continuum and is associated with symptom severity, chronicity, and poorer treatment prognosis.[18] There is still a great lack of knowledge with regard to psychotic and schizotypal symptoms among patients with OCD and how these symptoms affect psychological treatment of OCD. In addition, we do not know whether treatment for OCD reduces psychotic and schizotypal symptoms.
In the current study we assessed psychotic and schizotypal symptoms among non-psychotic patients with OCD. Furthermore, this study aimed to elucidate whether such symptoms are elevated in the OCD population, or similarly present in a general non-psychotic psychiatric outpatient sample. Finally, the current study aimed to investigate whether such symptoms were associated with reduced OCD treatment response, and if these symptoms are reduced following exposure and response prevention treatment (ERP).
