Psychopathologic differences between cannabis-induced psychoses and recent-onset primary psychoses with abuse of cannabis Gabriel Rubio a,b,c, ⁎ , Jesús Marín-Lozano d , Francisco Ferre b,e , Isabel Martínez-Gras a,b,c , Roberto Rodriguez-Jimenez a,b,c , Javier Sanz a,b,c , Miguel Angel Jimenez-Arriero a,b,c , José Luis Carrasco b,c,f , David Lora g , Rosa Jurado a,c , José Ramón López-Trabada a , Tomás Palomo a,b,c a 12 de Octubre University Hospital, Madrid, Spain b Department of Psychiatry, Faculty of Medicine, Complutense University, Madrid, Spain c Biomedical Research Center Network for Mental Health (CIBERSAM), Madrid, Spain d La Paz University Hospital, Madrid, Spain e Gregorio Marañón University Hospital, Madrid, Spain f Clínico San Carlos University Hospital, Madrid, Spain g Clinical Epidemiology Research Unit, 12 de Octubre University Hospital, Madrid, Spain Abstract The study aims to identify psychopathologic variables in cannabis-induced psychosis and recent-onset primary psychoses using the Symptom Checklist-90-R and the Psychiatric Research Interview for Substance and Mental Disorders. A sample of 181 subjects with psychotic symptoms and cannabis use referred to the psychiatry inpatient units of 3 university general hospitals were assessed. The final sample included 50 subjects with a diagnosis of cannabis-induced psychotic disorder (CIPD) and 104 subjects with primary psychotic disorders. Using receiver operating characteristic curves, the most efficient psychopathologic variables for classifying CIPD were interpersonal sensitivity, “depression,” phobic anxiety, and Scale to Assess Unawareness of Mental Disorders subscales. The area under the receiver operating characteristic curve of the model including depression and “misattribution” scores was 96.78% (95% confidence interval, 94.43-99.13). Depressive symptoms could be used to distinguish CIPD from other primary psychotic disorders. Clinical variables related to “neurotic” symptoms could be involved in the susceptibility to cannabis-induced psychosis. © 2012 Elsevier Inc. All rights reserved. 1. Introduction Cannabis use is widespread in the general population of the United States, European Union, and Spain [1-3]. It is also common in subjects with severe mental disorders [4,5]. The association between cannabis use and psychoses is well- known [4,6,7]. Cannabis use provokes induced psychosis [8], and in subjects with schizophrenia, cannabis abuse was related to earlier onset [9], worse prognosis [10-13], and cognitive impairment [14,15]. In some cases, cannabis can increase the susceptibility for a state of chronic psychosis [16]. Cannabis use is also very common in patients with bipolar disorders (BDs) [17-19]; it is associated with an earlier age at onset [20], lower compliance, and higher levels of overall illness severity [21,22]. The similarities between the clinical features of cannabis- induced psychotic disorder (CIPD) and recent-onset primary psychoses (mainly schizophrenia) with concurrent cannabis use give rise to diagnostic and management difficulties in patients with these disorders [23]. Recent studies have attempted to establish the clinical differences between CIPD and primary psychotic disorders (PPDs) (see review by Mathers et al [5]); however, these have either been cross- sectional studies in which the symptoms of the 2 disorders have been compared [24-26] or else follow-up studies to determine which patients are finally diagnosed with Available online at www.sciencedirect.com Comprehensive Psychiatry 53 (2012) 1063 – 1070 www.elsevier.com/locate/comppsych Conflict of interest: None. ⁎ Corresponding author. Hospital Universitario 12 de Octubre, Glorieta de Málaga s/n, 28041 Madrid, Spain. Tel.: +34 913908022; fax: +34 913908538. E-mail address: gabrielrubio@med.ucm.es (G. Rubio). 0010-440X/$ – see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.comppsych.2012.04.013