title: Concurrent and simultaneous polydrug use among young Swiss males: use patterns and associations of number of substances used with health issues.
abstract: BACKGROUND
  Simultaneous polydrug use (SPU) may represent a greater incremental risk factor for human health than concurrent polydrug use (CPU). However, few studies have examined these patterns of use in relation to health issues, particularly with regard to the number of drugs used.
  
  
  METHODS
  In the present study, we have analyzed data from a representative sample of 5734 young Swiss males from the Cohort Study on Substance Use Risk Factors. Exposure to drugs (i.e., alcohol, tobacco, cannabis, and 15 other illicit drugs), as well as mental, social and physical factors, were studied through regression analysis.
  
  
  RESULTS
  We found that individuals engaging in CPU and SPU followed the known stages of drug use, involving initial experiences with licit drugs (e.g., alcohol and tobacco), followed by use of cannabis and then other illicit drugs. In this regard, two classes of illicit drugs were identified, including first uppers, hallucinogens and sniffed drugs; and then "harder" drugs (ketamine, heroin, and crystal meth), which were only consumed by polydrug users who were already taking numerous drugs. Moreover, we observed an association between the number of drugs used simultaneously and social issues (i.e., social consequences and aggressiveness). In fact, the more often the participants simultaneously used substances, the more likely they were to experience social problems. In contrast, we did not find any relationship between SPU and depression, anxiety, health consequences, or health.
  
  
  CONCLUSIONS
  We identified some associations with SPU that were independent of CPU. Moreover, we found that the number of concurrently used drugs can be a strong factor associated with mental and physical health, although their simultaneous use may not significantly contribute to this association. Finally, the negative effects related to the use of one substance might be counteracted by the use of an additional substance.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Baggio
authors.forename: Joseph
authors.initials: J
authors.lastname: Studer
authors.forename: Meichun
authors.initials: M
authors.lastname: Mohler-Kuo
authors.forename: Jean-Bernard
authors.initials: JB
authors.lastname: Daeppen
authors.forename: Gerhard
authors.initials: G
authors.lastname: Gmel
mesh_terms: D000293:Adolescent; D017668:Age of Onset; D000428:Alcohol Drinking / Q000453:epidemiology*; D055030:Drug Users / Q000145:classification*; D006801:Humans; D013287:Illicit Drugs; D008297:Male; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology*; D019966:Substance-Related Disorders / Q000453:epidemiology*; D013557:Switzerland / Q000453:epidemiology; D055815:Young Adult
chemical_list: D013287:Illicit Drugs