Neurobiology of Comorbid Substance Use Disorders in Mental Illness: A Closer Look at the Underlying Commonalities between Cannabis and Schizophrenia

The high rate of cannabis use disorders (CUDs) among patients with schizophrenia is well established. The implications of this comorbidity are extensive and include symptom exacerbation, frequent relapses leading to hospitalization and an overall worsening of prognosis. Therefore, a greater understanding of why cannabis use and schizophrenia frequently present in the same individual is critical. In this article, we propose that common neurobiological pathways and substrates independently contribute to the predisposition of developing these disorders. Dysregulation of the endocannabinoid system, as well as abnormalities in neurophysiology, neurocognition, genetics, and brain morphology may contribute to this comorbidity. Future studies are needed to confirm these commonalities between CUDs and schizophrenia, given that better understanding of their etiology may guide integrated treatment interventions and the development of prevention strategies for these prevalent comorbid disorders.