The positive association between substance use and sexual activity, or risky sexual behavior, is not causal and more likely attributable to some other variables..
Rates of teen pregnancy and out-of-wedlock birth in the United States are high, the latter having risen from seven per 1000 in 1940 to 46 per 1000 in 1994.The current rates are nearly twice those of Britain and Canada. And, survey data indicate that in 1999, 25 percent of sexually active students had used alcohol or drugs at the time of their last sexual intercourse.
In Get High and Get Stupid: The Effect of Alcohol and Marijuana Use on Teen Sexual Behavior (NBER Working Paper No. 9216), co-authors Michael Grossman, Robert Kaestner, and Sara Markowitz investigate whether use of alcohol and marijuana cause sexual activity and risky sexual behavior. They argue that, while the overwhelming majority of studies show a positive correlation between alcohol and marijuana use and sexual activity, those studies do not establish a causal relationship. Their results suggest that the positive association between substance use and sexual activity, or risky sexual behavior, is not causal and more likely attributable to some other variables.
One alternative explanation for the positive association between substance use and sexual activity is that these behaviors may reflect a common personality trait, such as thrill-seeking behavior. Another possible explanation is that a teenager who chooses to have many sexual partners may use drugs to cope with society's negative view of such behavior, thereby lowering the psychic costs of risky sex.
The authors also point out that for many reasons the large number of studies has not been able to establish causality. For example, these studies typically use non-representative samples, and, most of these studies fail to control for a variety of family background and personal factors that may confound estimates of the relationship between substance abuse and sexual practices. Finally, no prior study has recognized the possibility that reverse causality may be at work; that is, that sexual activity may actually cause substance abuse.
The authors data come from two sources: the 1997 cohort of the National Longitudinal Survey of Youth (NLSY97), which consists of approximately 8,500 youth between the ages of 12 and 16; and the National Longitudinal Survey of Adolescent Health, which consists of approximately 6,000 youth in grades seven through twelve.
-- Les Picker