title: Use transition between illegal drugs among Brazilian university students.
abstract: OBJECTIVE
  The aim of the present study was to test whether the first use of an illicit drug increases the chance of first use of other illicit drugs.
  
  
  METHODS
  The transitions from the first use of a drug to the first use of another drug were analyzed. Comparisons were made between first drug users and non-users. Survival analysis methods were used to compare the cumulative probability of second drug use after adjusting for socio-demographic covariates and the intermediate use of alcohol and/or tobacco. A total of 12,721 Brazilian university students participated in this study.
  
  
  RESULTS
  Inhalants and marijuana were used prior to the use of several other drugs, whereas the opposite pattern was not found. Ecstasy was used before other drugs in several instances. Other well-examined drugs, such as amphetamines, cocaine and hallucinogens, were used both before and after other illicit drugs without any marked predominance for either of the two roles.
  
  
  CONCLUSIONS
  This study supports the role of the use of marijuana and inhalants almost exclusively before the use of other illicit drugs, whereas the use of ecstasy has an opposite role. These roles could be linked to the prevalence of lifetime use and whether individuals were at an earlier or later age during experimentation.
authors.affiliation: Interdisciplinary Group of Studies on Alcohol and Drugs (GREA), Institute of Psychiatry, Medical School, University of São Paulo, Rua Dr. Ovídio Pires de Campos, 785 (GREA), São Paulo, SP, 05403-903, Brazil, jmcmaia2@gmail.com.
authors.forename: João Mauricio
authors.initials: JM
authors.lastname: Castaldelli-Maia
authors.forename: Silvia S
authors.initials: SS
authors.lastname: Martins
authors.forename: Lúcio Garcia
authors.initials: LG
authors.lastname: de Oliveira
authors.forename: Margriet
authors.initials: M
authors.lastname: van Laar
authors.forename: Arthur Guerra
authors.initials: AG
authors.lastname: de Andrade
authors.forename: Sergio
authors.initials: S
authors.lastname: Nicastri
mesh_terms: D000293:Adolescent; D001938:Brazil / Q000453:epidemiology; D055030:Drug Users / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D013287:Illicit Drugs; D008297:Male; D015995:Prevalence; D013334:Students / Q000523:psychology / Q000706:statistics & numerical data*; D014495:Universities / Q000706:statistics & numerical data*; D055815:Young Adult
chemical_list: D013287:Illicit Drugs
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