title: Real-time electronic ambulatory monitoring of substance use and symptom expression in schizophrenia.
abstract: OBJECTIVE
  Despite evidence demonstrating elevated comorbidity between schizophrenia and substance use disorders, the underlying mechanisms of association remain poorly understood. The brief time intervals that characterize interactions between substance use and psychotic symptoms in daily life are inaccessible to standard research protocols. The authors used electronic personal digital assistants (PDAs) to examine the temporal association of diverse forms of substance use with psychotic symptoms and psychological states in natural contexts.
  
  
  METHODS
  Of 199 community-dwelling individuals with schizophrenia or schizoaffective disorder who were contacted to participate in the study, 92% accepted and 73% completed the study. The 145 participants who completed the study provided reports of substance use, psychotic symptoms, mood, and event negativity multiple times per day over 7 consecutive days through PDAs.
  
  
  RESULTS
  Participants responded to 72% of the electronic interviews (N=2,737) across daily life contexts. Strong within-day prospective associations were observed in both directions between substance use and negative psychological states or psychotic symptoms, but considerable variation was observed by substance type. Consistent with the notion of self-medication, alcohol use was most likely to follow increases in anxious mood or psychotic symptoms. Cannabis and other illicit substances, demonstrating more complex patterns, were more likely to follow certain psychological states but were also associated with the later onset of psychotic symptoms.
  
  
  CONCLUSIONS
  The dynamic interplay of substance use and psychotic symptoms is in many cases consistent with both causal and self-medication mechanisms, and these patterns of association should be considered in the design of treatment and prevention strategies.
authors.affiliation: National Center for Scientific Research, CNRS UMR, Bordeaux, France. joel.swendsen@u-bordeaux2.fr
authors.forename: Joel
authors.initials: J
authors.lastname: Swendsen
authors.forename: Dror
authors.initials: D
authors.lastname: Ben-Zeev
authors.forename: Eric
authors.initials: E
authors.lastname: Granholm
mesh_terms: D000328:Adult; D000428:Alcohol Drinking / Q000009:adverse effects* / Q000453:epidemiology*; D015897:Comorbidity; D034201:Computers, Handheld; D005260:Female; D006801:Humans; D013287:Illicit Drugs / Q000633:toxicity*; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology; D008875:Middle Aged; D018670:Monitoring, Ambulatory; D011569:Psychiatric Status Rating Scales; D011605:Psychoses, Substance-Induced / Q000453:epidemiology*; D011618:Psychotic Disorders / Q000453:epidemiology*; D012559:Schizophrenia / Q000139:chemically induced* / Q000453:epidemiology*; D012651:Self Medication / Q000523:psychology; D019966:Substance-Related Disorders / Q000453:epidemiology*
chemical_list: D013287:Illicit Drugs