title: Drinking with mixed-gender groups is associated with heavy weekend drinking among young adults.
abstract: To investigate how gender composition of the drinking group affects young adults' alcohol consumption on weekend evenings over and above the effect of drinking-group size.
  
  
  
  Using the internet-based cellphone-optimized assessment technique (ICAT), participants completed online questionnaires on their cell phones every hour from 8 p.m. to midnight on Thursday, Friday and Saturday evenings during five consecutive weekends.
  
  
  
  French-speaking Switzerland.
  
  
  
  Convenience sample of 183 young adults (53.0% female, mean age = 23.1) who completed a total of 4141 hourly assessments.
  
  
  
  Alcohol consumption and number of male and female friends present assessed at 8 p.m., 9 p.m., 10 p.m., 11 p.m. and midnight.
  
  
  
  Results of three-level negative binomial regression analyses showed that women consumed significantly more drinks per hour when drinking in mixed-gender groups (Z-values ranging from 2.9 to 5.3, all P < 0.01) and significantly fewer drinks when drinking with men only (Z = -2.7, P < 0.01), compared with drinking with women only. Men reported consuming more drinks per hour in mixed-gender groups of equal gender composition (Z = 2.4, P < 0.05) or mixed-gender groups with men in the majority (Z = 2.2, P < 0.05) and fewer hourly drinks when drinking with women only (Z = -4.9, P < 0.001), compared with drinking with men only. Drinking-group size predicted the hourly number of drinks for women (Z = 6.0, P < 0.001) and men (Z = 5.5, P < 0.001).
  
  
  
  Drinking-group gender composition is associated with number of drinks consumed per hour, over and above the impact of the drinking-group size. Young adults report consuming more drinks per hour when drinking with mixed-gender groups than with same-gender groups.
authors.affiliation: Center for Tobacco Control Research and Education, University of California, San Francisco, CA, USA.
authors.forename: Johannes
authors.identifier: 0000-0001-8929-9579
authors.initials: J
authors.lastname: Thrul
authors.affiliation: Addiction Switzerland, Research Institute, Lausanne, Switzerland.
authors.forename: Florian
authors.initials: F
authors.lastname: Labhart
authors.affiliation: Addiction Switzerland, Research Institute, Lausanne, Switzerland.|Behavioural Science Institute, Radboud University, Nijmegen, the Netherlands.|Faculty of Education and Psychology, Eötvös Loránd University, Budapest, Hungary.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Kuntsche
mesh_terms: D000328:Adult; D063425:Binge Drinking / Q000453:epidemiology*; D005260:Female; D033062:Friends; D006801:Humans; D007899:Leisure Activities; D008297:Male; D017678:Sex Distribution; D012931:Social Environment; D011795:Surveys and Questionnaires; D013557:Switzerland / Q000453:epidemiology; D055815:Young Adult
keywords: Alcohol use; event-level; gender; group composition; multi-level models; young adults