Males are more likely than females to abuse drugs. According to the 1999 National Household Survey on Drug Abuse (NHSDA)-an annual Substance Abuse and Mental Health Services Administration survey of more than 25,000 respondents-8.1 percent of males and 4.5 percent of females older than age 12 had used illicit drugs within the past month, and this ratio has remained fairly constant throughout the 29-year history of the survey. Research by Dr. James Anthony, a NIDA-supported scientist at the Johns Hopkins University School of Hygiene and Public Health in Baltimore, shows that these gender differences in drug abuse are not related to gender differences in susceptibility. Instead, they have their foundation in the very first stage of drug involvement-the opportunity to use drugs. Once given the opportunity to use, males and females are equally likely to use drugs.

Dr. Anthony and his colleagues analyzed NHSDA data for 1993 to look for information that might explain the gender difference in rates of drug abuse. "Males are more likely than females to have an opportunity to use drugs. There is no male-female difference with respect to trying a drug once an opportunity to do so has been experienced," Dr. Anthony says.

According to the 1993 National Household Survey on Drug Abuse, boys are more likely to abuse drugs than girls. The graph above shows the estimated percentage of boys and girls using each drug and the percentage having the opportunity to use each drug.

The findings are consistent for marijuana, cocaine, hallucinogens, and heroin, Dr. Anthony says. The proportion of opportunities to use marijuana was 59 percent of males compared with 43.9 percent of females; to use cocaine, 28.7 percent of males and 18.3 percent of females; to use hallucinogens, 18.6 percent of males and 10 percent of females; and to use heroin, 7.8 percent of males and 3.2 percent of females.

Once presented with an opportunity to use drugs, 44.2 percent of males and 42 percent of females began using marijuana within 1 year; 37.7 percent of males and 33.2 percent of females began using cocaine; 50.5 percent of males and 50 percent of females began using hallucinogens; and 14.6 percent of males and 22.1 percent of females began using heroin.

This graph shows the percentage of drug use within 1 year of the first opportunity to use drugs and the percentage of boys and girls to eventually use drugs, given the opportunity.

Dr. Anthony found that females were likely to get their first opportunity to use cocaine at an earlier age than were males (age 19 for females, age 20 for males) but that there were no differences among males and females in age of first opportunity to use marijuana, heroin, or hallucinogens.

One benefit of improved understanding of the link between opportunity and eventual use is that counselors or physicians may be able to learn about young patients' drug use by asking about their opportunities to use drugs. "Young people may feel freer to answer a question about the opportunity to use drugs rather than a question about actual drug use, because the opportunity is less likely to be illegal or particularly sensitive," Dr. Anthony says.

Understanding the differences in opportunities to use drugs may also help shape prevention efforts, according to Dr. Cora Lee Wetherington, NIDA's Women and Gender Research Coordinator. "The prevalence of drug abuse is greater for males than for females even though, given the initial opportunity to use drugs, males and females are equally likely to move on to drug use. It appears that the opportunities themselves play a very important role in drug abuse and need more investigation. Understanding the sex differences in opportunities could make it possible to develop prevention programs that reduce the opportunities and, therefore, the higher rate of drug abuse among males. In fact, NIDA-supported research into sex differences in opportunities (see "Boys and Girls Encounter Different Drug Offers, Use Different Refusal Strategies") raises the possibility that gender-specific prevention interventions that focus on drug opportunities could serve to reduce drug use by both males and females," Dr. Wetherington says.

Sources

Van Etten, M.L., and Anthony, J.C. Comparative epidemiology of initial drug opportunities and transitions to first use: marijuana, cocaine, hallucinogens and heroin. Drug and Alcohol Dependence 54:117-125, 1999.

Van Etten, M.L.; Neumark, Y.D.; and Anthony, J.C. Male-female differences in the earliest stages of drug involvement. Addiction 94(9):1413-1419, 1999. [Abstract]