title: A comparison of psychotic symptoms in subjects with methamphetamine versus cocaine dependence.
abstract: The psychostimulant drugs cocaine and methamphetamine are potent indirect dopamine receptor agonists which act through similar but not identical mechanisms. Studies in humans have observed that a large proportion of those who chronically use these drugs experience psychotic symptoms. However, direct comparisons of psychotic symptom severity between cocaine and methamphetamine users are lacking.
  
  
  
  The goal of the present study was to directly compare severity of psychotic symptoms between cocaine- and methamphetamine-dependent individuals. Additionally, we sought to determine how concurrent cocaine + methamphetamine dependence would influence psychotic symptoms.
  
  
  
  We recruited 153 polysubstance-using subjects meeting DSM-IV-TR criteria for cocaine dependence, 38 with methamphetamine dependence, and 32 with cocaine + methamphetamine dependence. Psychotic symptoms were assessed with the Positive and Negative Syndrome Scale (PANSS) and analyzed using a five-factor model. All participants were also assessed for physical and mental illnesses as well as recent substance use. Most subjects completed a comprehensive neurocognitive battery.
  
  
  
  While all three groups exhibited high total PANSS scores, the positive symptom subscale was significantly higher in the methamphetamine-dependent (17.03 ± 6.3) than the cocaine-dependent group (13.51 ± 4.12) and non-significantly higher (p = 0.08) than the cocaine + methamphetamine group (14.44 ± 5.50). Groups also differed on demographic variables, viral infection, and other indices of substance use, which were unlikely to account for the difference in positive symptoms. There were only modest differences between groups in neurocognitive function.
  
  
  
  Methamphetamine dependence was associated with more severe positive symptoms of psychosis than cocaine dependence. Concurrent cocaine + methamphetamine dependence did not increase psychosis severity.
authors.affiliation: Department of Pharmacology, 2176 Health Sciences Mall, University of British Columbia, Vancouver, B.C., V6T 1Z3, Canada.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Alexander
authors.affiliation: Department of Psychology, Simon Fraser University, Burnaby, B.C., V5A 1S6, Canada.
authors.forename: Kristina M
authors.initials: KM
authors.lastname: Gicas
authors.affiliation: Department of Psychology, Simon Fraser University, Burnaby, B.C., V5A 1S6, Canada.
authors.forename: Taylor S
authors.initials: TS
authors.lastname: Willi
authors.affiliation: Department of Pharmacology, 2176 Health Sciences Mall, University of British Columbia, Vancouver, B.C., V6T 1Z3, Canada.
authors.forename: Clara N
authors.initials: CN
authors.lastname: Kim
authors.affiliation: Department of Psychiatry, University of British Columbia, Vancouver, B.C., V6T 1Z3, Canada.
authors.forename: Veronika
authors.initials: V
authors.lastname: Boyeva
authors.affiliation: Department of Psychiatry, University of British Columbia, Vancouver, B.C., V6T 1Z3, Canada.
authors.forename: Ric M
authors.initials: RM
authors.lastname: Procyshyn
authors.affiliation: Department of Psychiatry, University of British Columbia, Vancouver, B.C., V6T 1Z3, Canada.
authors.forename: Geoff N
authors.initials: GN
authors.lastname: Smith
authors.affiliation: Department of Psychology, Simon Fraser University, Burnaby, B.C., V5A 1S6, Canada.
authors.forename: Allen E
authors.initials: AE
authors.lastname: Thornton
authors.affiliation: Department of Psychiatry, University of British Columbia, Vancouver, B.C., V6T 1Z3, Canada.
authors.forename: William J
authors.initials: WJ
authors.lastname: Panenka
authors.affiliation: Department of Psychiatry, University of British Columbia, Vancouver, B.C., V6T 1Z3, Canada.
authors.forename: Andrea A
authors.initials: AA
authors.lastname: Jones
authors.affiliation: Department of Psychiatry, University of British Columbia, Vancouver, B.C., V6T 1Z3, Canada.
authors.forename: Fidel
authors.initials: F
authors.lastname: Vila-Rodriguez
authors.affiliation: Department of Radiology, University of British Columbia, Vancouver, B.C., V6T 1Z3, Canada.
authors.forename: Donna J
authors.initials: DJ
authors.lastname: Lang
authors.affiliation: Department of Psychiatry, University of British Columbia, Vancouver, B.C., V6T 1Z3, Canada.
authors.forename: G
authors.initials: G
authors.lastname: William MacEwan
authors.affiliation: Department of Psychiatry, University of British Columbia, Vancouver, B.C., V6T 1Z3, Canada.
authors.forename: William G
authors.initials: WG
authors.lastname: Honer
authors.affiliation: Department of Pharmacology, 2176 Health Sciences Mall, University of British Columbia, Vancouver, B.C., V6T 1Z3, Canada. al.barr@ubc.ca.
authors.forename: Alasdair M
authors.initials: AM
authors.lastname: Barr
mesh_terms: D000328:Adult; D019969:Amphetamine-Related Disorders / Q000175:diagnosis / Q000523:psychology*; D000697:Central Nervous System Stimulants; D019970:Cocaine-Related Disorders / Q000175:diagnosis / Q000523:psychology*; D015331:Cohort Studies; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008694:Methamphetamine; D008875:Middle Aged; D011605:Psychoses, Substance-Induced / Q000175:diagnosis / Q000523:psychology*
chemical_list: D000697:Central Nervous System Stimulants; D008694:Methamphetamine
keywords: Cocaine; Dependence; Methamphetamine; Neurocognition; PANSS; Psychosis; Psychostimulant; Substance use; Symptom severity