Short Communication Predictors of psychosis severity in individuals with primary stimulant addictions Bonnie Lichlyter a, ⁎, Scot Purdon a,b,c , Philip Tibbo a,d a Department of Psychiatry, University of Alberta, 1E7.11 WMC, 8440 112th St, Edmonton, AB, Canada T6G 2B7 b Edmonton Early Psychosis Intervention Clinic, 5th Floor, 9942 108 Street, Edmonton, AB, Canada T5K 2J5 c Bebensee Schizophrenia Research Unit, Box 307, 17480 Fort Road, Alberta Hospital Edmonton, Edmonton, AB, Canada T5J 2J7 d Department of Psychiatry, Dalhousie University, 5909 Veteran's Memorial Lane, 8th floor, Halifax, Nova Scotia, Canada B3H 2E2 abstract article info Keywords: Drug abuse Psychosis Methamphetamine The goal of this study is to define the factors that could contribute to the development, severity, and persistence of psychotic symptoms in individuals with stimulant addiction. We hypothesize that particular drug use variables may contribute to the severity of psychiatric symptoms. Thirty-seven stimulant users, abstinent for N 30 days were recruited from the community. Previous drug use and current and past psychiatric symptoms were assessed using validated objective rating scales and several self-report questionnaires. Age at first use of the stimulant drug was inversely related to the Beck Anxiety Inventory score, and the subjects with more than 5 years duration of chronic use exhibited greater severity of symptoms on the PANSS Positive and General Scales and total score. The method of drug administration, duration of abstinence, latency from first use to regular use, and prior solicitation of treatment were not related to PANSS total and subscale scores or other clinical variables. Severity of psychosis appears to be related to earlier and longer exposure to stimulants, consistent with a “threshold” effect of stimulant use on the development of psychotic symptoms. The association may also suggest a critical developmental period that is most susceptible to the deleterious effects of stimulant exposure. © 2010 Elsevier Ltd. All rights reserved. 1. Introduction The comorbidity of drug abuse and psychotic disorders is a major problem for clinicians and treatment centres, with recent studies suggesting 70–80% of individuals presenting with schizophrenia also present with a comorbid substance dependence disorder (Westermeyer, 2006), and patients with schizophrenia are up to 5.3 times more likely to have substance use disorders than persons without mental illness (Cantor-Graae, Nordstrom, & McNeil, 2001). Nicotine and alcohol are the most commonly abused substances by persons with schizophrenia (Volkow, 2009), followed by cannabis and then stimulant use (cocaine or amphetamines; Coyle, 2006). Despite the compelling evidence of an association between substance use and schizophrenia, few investigations have success- fully described a temporal precedence or direction for this association, a minimum requirement for assessment of causality (Mueser, Noordsy, Drake, & Fox, 2003). The ambiguity in causation is particularly problematic in regard to stimulant use because many stimulants can induce relatively persistent psychotic states that appear to mimic the symptoms of schizophrenia. Most noteworthy is methamphetamine (MA), a stimulant that can lead to a psychotic state that persists beyond intoxication and excretion. MA induces feelings of euphoria, increased energy, decreased appetite and a decreased need for sleep, making it a common drug of choice among street people and youth, a demo- graphic at elevated risk for a first episode of schizophrenia. Differential diagnosis between schizophrenia and MA psychosis is thus particularly important in younger samples suffering a first episode of psychosis, though sensitive and specific criteria for this differential are not available. MA psychosis is characterized by a paranoid hallucinatory state that develops gradually with repeated MA abuse and continues after MA withdrawal (Sweeting & Farrell, 2005). As many as 10% of chronic MA users develop a persistent psychotic disorder, while at least 23% develop clinically significant psychotic symptoms (McKetin, McLaren, Lubman, & Hides, 2006). The primary characteristic of MA psychosis is a higher positive to negative symptom ratio than de novo schizophre- nia (Srisurapanont et al., 2003), but other features relevant to a differential diagnosis remain unclear. There is a dearth of predictive characteristics with a confirmed relation to the relative risk of psychosis among MA users. Several recent studies have offered preliminary data suggesting a number of potentially relevant demographic, psychological, familial and Addictive Behaviors 36 (2011) 137–139 Abbreviations: MA, methamphetamine; SIPs, substance-induced psychosis; BDI, Beck Depression Inventory; BAI, Beck Anxiety Inventory; MIS, Magical Ideation Scale; SAS, Social Anhedonia Scale; SCID, Structured Clinical Interview for DSM-IV-TR; PANSS, Positive and Negative Syndrome Scale. ⁎ Corresponding author. Tel.: + 1 780 492 6033; fax: + 1 780 407 6672. E-mail addresses: lichlyte@ualberta.ca (B. Lichlyter), scot.purdon@albertahealthservices.ca (S. Purdon), phil.tibbo@cdha.nshealth.ca (P. Tibbo). 0306-4603/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.addbeh.2010.08.019 Contents lists available at ScienceDirect Addictive Behaviors