Chiao et al. BMC Public Health 2012, 12:527 http://www.biomedcentral.com/1471-2458/12/527 Page 6 of 10 Table 1 Sample characteristics for male and female college youth (percentage or mean), TYP (Continued) Family structure: Lives with both biological parents Yes No Yes No Yes No Yes No Yes No Yes No Yes No Yes No Perceived family support School work Economic difficulty Emotional difficulty Perceived friend support School work Economic difficulty Emotional difficulty Premarital sex in college Involvement in premarital sex by age 22 80.8 19.3 64.3 35.7 87.3 12.7 44.6 55.4 79.9 20.1 25.4 74.6 85.1 14.9 28.1 71.9 72.2 27.8 57.6 42.5 84.0 16.0 31.6 68.4 82.1 17.9 36.3 63.7 91.0 9.0 – – 61.5 38.5 55.4 44.6 83.1 16.9 50.0 50.0 80.0 20.0 46.2 53.9 93.9 6.2 – – 82.0 18.1 60.1 39.9 85.6 14.4 38.4 61.6 74.8 25.2 24.2 75.9 78.7 21.3 20.2 79.8 84.2 15.8 70.6 29.4 90.0 10.0 52.1 47.9 83.8 16.2 21.2 78.8 88.2 11.8 13.1 86.9 Note: Participants who missed responses on covariates were excluded. Percentages may not add up to 100 due to rounding. counterparts. In addition, for those abstinent youth, the predictive effect of adolescent cigarette and alcohol use differed for male and female. For males, adolescent “heavier drinking” was significantly related to later pre- marital sex (by age 22); however, for females, adolescent “light drinking” was significantly associated with later premarital sex. These results are consistent with previ- ous findings of a positive association between alcohol use and premarital sexual activity [12,29,30]. Our ana- lyses further suggest gender differences in a dose–re- sponse effect in which the likelihood of later premarital sex is associated with heavier drinkers in males vs. light drinkers in females. And, these results imply that females may suffer more than males from being alco- holic in social norms. The finding of no significant pre- dictive effect of cigarette smoking on self-reported premarital sex for females is consistent with previous reports [31,32], but the significant predictive effect of cigarette smoking for males differs from the existing literature. This might be because the adolescent smoking rate is much lower among females in the sample (2%) than for males (8%). It is recommended future research studies examine how/if adolescent cigarette use links to female sexual activities. Our findings are consistent with the Theory of Planned Behavior and its emphasis on cultural norms and attitudes as related to attitudes toward premarital sex. Previous studies found adolescent premarital sexual activity to be shaped by or associated with contextual factors [8,33-35]. These contextual factors (e.g., school attendance and community participation) impose con- ventional behavioral expectations with adolescents expected to abstain from sex until marriage. Prior re- search also showed a significant association between lib- eral attitudes toward premarital sex and premarital sexual activity in Nepal college males [36]. In our college sample, those adolescents with permissive premarital sexual attitudes were more likely to engage in premarital