The relationship of substance use to sexual activity among young adults in the United States.

Data on substance use and sexual activity from a nationally representative, probability-based sample of young adults aged 18-30 in 1990 indicate that 86% of respondents had had sex in the previous 12 months, with three-fourths reporting no more than one sexual partner. Seventy-five percent of respondents had consumed alcohol in the past 12 months, 40% had smoked cigarettes and 20% had used marijuana. After adjustment for demographic factors, both sexual activity and a history of multiple partners were positively associated with some measures of substance use. Respondents who drank more frequently, those who were heavy drinkers, those who smoked cigarettes and those who used marijuana in the past year were more likely than others to be sexually active. Those who consumed five or more drinks at a sitting and those who used marijuana were more likely than others to have had more than one sexual partner. Heavy drinkers were also less likely to use condoms; however, the results showed no association between having sex under the influence of alcohol and engaging in unsafe sexual practices.