The association between obsessive-compulsive disorder (OCD) or symptoms (OCS) and schizophrenia has been accounted in literature for more than hundred years. Early conceptions stated that OCD could be a 'neurotic defence' or a protection against incipient psychosis. In spite of that, during many decades both pathologies were held as unrelated, namely because their phenomenological differences and because only few cases of OCD developed into psychosis. Nevertheless, OCS are present in many cases of schizophrenia, sometimes as first symptoms. Recently the hypothesis of OCD and schizophrenia being related is seen with more plausibility since they share same neurobiological pathways. Intrusive thoughts and delusions may form a continuum making, perhaps, OCD and schizophrenia two extremes of a spectrum.

To preform a non-systematic review about the relation of OCD with schizophrenia

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OCD and schizophrenia co-morbidity has a prevalence six times higher than expected. OCD could be present in a psychotic prodrome. In some studies, both pathologies appeared to be risk factors for the development of each other. Moreover they appear to share some neurobiological correlates and neuropsychological aspects.

OCD and schizophrenia could be correlated and may be at extreme points of a spectrum of pathologies with intermediate clinical manifestations.