Obsessions and Delusions: The Clinical Overlap and Differential Diagnosis of Obsessive-Compulsive and Psychotic Disorders

Abstract

Obsessive-compulsive symptoms (OCS) are commonly observed in the pre-illness, prodromal, first-episode, and chronic stages of schizophrenia. Similarly, patients with obsessive-compulsive disorder (OCD) can present with delusional levels of conviction that border on psychosis. Transitions between OCD and schizophrenia spectrum disorders are also common. The phenomenological overlap between obsessions and delusions can be challenging for accurate diagnosis and treatment planning. Clinicians may struggle to differ entiate obsessions from delusions in severe OCD and similarly may not know if the emerging obsessive symptoms in schizophrenia require specialized OCD treatment. This review summarizes the current literature on comorbid obsessive-compulsive and psychotic disorders, transitions between these two disorders, the impact on prognosis, and the clinical strategies in differential diagnosis as well as treatment planning. [ Psychiatr Ann . 2023;53(5):199–203.]