Background: Childhood trauma (CT) and cannabis use are both environmental and modifier risk factors for schizophrenia. However, little is known about how they interact in schizophrenia. We examined the main effect of each of these two environmental factors on the clinical expression of the disease using a large set of variables, and we tested whether and how cannabis and CT interact to influence the course and the presentation of the illness.
Methods: A sample of 366 patients who met the DSM-IV-TR criteria for schizophrenia was recruited through the FACE-SCZ (Fondamental Advanced Centre of Expertise - Schizophrenia) network. Patients completed a large standardized clinical evaluation including Structured Clinical Interview for DSM Disorders-I (SCID-I), Positive and Negative Symptoms Scale (PANSS), Columbia-Suicide Severity Rating Scale (C-SSRS), Global Assessment of Functioning (GAF), Short-Quality of Life-18 (S-QoL-18), and Medication Adherence Rating Scale (MARS). We assessed CT with the Childhood Trauma Questionnaire and cannabis status with SCID-I.
Results: CT significantly predicted the number of hospitalizations, GAF, and S-QoL-18 scores, as well as the PANSS total, positive, excitement, and emotional distress scores. Cannabis use disorders significantly predicted age of onset, and MARS. There was no significant interaction between CT and cannabis use disorders. However, we found evidence of a correlation between these two risk factors.
Conclusions: CT and cannabis both have differential deleterious effects on clinical and functional outcomes in patients with schizophrenia. Our results highlight the need to systematically assess the presence of these risk factors and adopt suitable therapeutic interventions.
Keywords: Cannabis use disorder; Childhood trauma; Schizophrenia.
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