Evidence of a schizotypy subtype in OCD

OCD patients represent a heterogeneous mix of clinical phenotypes, likely reflecting a wide range of genetic vulnerabilities. In other medical illnesses, neurobiologically-based traits with a genetic component that are associated with the target disorder have been successfully used to detect patients with a specific genetic liability to disease. The overlap between symptoms of OCD and Schizophrenia suggested that schizotypal traits could have the potential to distinguish a relatively homogeneous subtype of OCD. We obtained schizotypy scores for 119 affected adult probands who met lifetime criteria for DSM-IV OCD. Five subscales from the Structured Interview of Schizotypy were used to assess ideas of reference, suspiciousness, magical thinking, illusions and psychotic-like thought. Selected for their obvious face validity with the cardinal signs of schizophrenia, Cronbach's alpha suggested that these subscales also provided a reliable measure of positive sign schizotypy (0.83). Fifty percent of our OCD sample had mild to severe positive schizotypy signs. t- and chi2 tests of significance suggested seven variables that distinguished OCD patients with schizotypy, including earlier age of onset, greater number of comorbid diagnoses and increased rates of learning disability, aggressive and somatic obsessions and counting and arranging compulsions. Three of these seven variables, including learning disabilities, counting compulsions and history of specific phobia, significantly increased the odds of schizotypy among patients with lifetime OCD. These findings enhanced the validity of the schizotypy construct in OCD. Whether this schizotypy subtype can distinguish a subgroup of patients with relatively homogeneous genetic characteristics waits further investigation.