, 2008; Rosendahl, Galanti, & Gilljam, 2008) and sales of snus are increasing in the United States (Biener, McCausland, Curry, & Sorafenib Tosylate price Cullen, 2011), examining how early experiences with snus impact future regular use is important. To our knowledge, no prior study has investigated this issue. Here we analyzed data from a large, population-based study in Sweden to describe reactions experienced during initial cigarette smoking and initial snus use. We applied binary recursive partitioning to evaluate how combinations of initial reactions may influence risk of becoming a regular user for each tobacco type. Methods Study Population The Swedish Twin study of Adults: Genes and Environment (STAGE; Lichtenstein et al., 2006) is a prospective, population-based study among 20,117 individuals from within the Swedish Twin Registry (http://ki.

se/twinreg; Pedersen, Lichtenstein, & Svedberg, 2002). Beginning in May 2005, 43,000 twins were invited to participate in the study and answer questions about common complex diseases and lifetime tobacco use history. The response rate for the baseline tobacco use assessment of STAGE was 47.0%; as described previously, higher proportions of nonparticipants were male, had at least one parent born outside of Sweden, had been convicted of a crime, had lower education levels, and had been diagnosed with a psychiatric disorder (Furberg et al., 2008). At baseline, information about use of cigarettes and snus were captured separately. Participants were asked about regularity of use (daily, occasional, just tried, or never) and status (current, former, never).

Smoking at least one cigarette per day for at least 1 month defined daily smoking and using at least one snus pouch per day for at least 1 month defined daily snus use. Participants were asked to recall their age(s) at first use of tobacco and the initial reactions associated with first trying each tobacco product. Tobacco use information was available from 19,073 participants, 55.2% of whom were women. Ages of participants ranged from 20 to 47 years and mean age at interview (��SD) was 33.4 (��7.7) years for men and 33.1 (��7.6) years for women. Nearly half of the STAGE sample had attended university (45.2%), and 63.7% were married or cohabitating. There were 5,466 complete twin pairs (N = 10,932; 57.3%). Overall, 60.7% of men and 63.3% of women ever smoked cigarettes, and 59.

9% of men and 25.4% of women ever used snus, prevalences comparable to other Swedish studies (Furberg et al., 2008). For the purposes of these Brefeldin_A cross-sectional analyses, we restricted the sample to 10,708 participants who either experimented with only cigarettes (EC; n = 4,297), experimented with only snus (ES; n = 1,737), or experimented with both cigarettes and snus during their lifetime (EC+S; n = 4,674). Participants were excluded if they never tried cigarettes or snus (n = 6,301), were missing all initial reaction data (n = 2,395), or were missing data on smoking status (n = 162) or sex (n = 10).