ANN ARBOR—The proportion of 35-year-olds who abuse alcohol and use illicit drugs is higher than might be expected, a University of Michigan study shows.

More than 32 percent of men report heavy drinking—defined as having five or more drinks in a row—at least once in the past two weeks. Nearly 13 percent of men and 7 percent of women report using marijuana in the past month, and 7 percent of men and 8 percent of women report misusing prescription drugs in the past year.

The study, published in the January 2004 issue of the American Journal of Public Health, uses data on 7,541 respondents from the Monitoring the Future study funded by the National Institute on Drug Abuse and conducted annually at the U-M Institute for Social Research (ISR) since 1975. The men and women who graduated from high school between 1977 and 1983 were randomly selected after graduation to participate in follow-up surveys every two years.

“We found that substance use was surprisingly prevalent at the start of midlife,” said Alicia Merline, an ISR researcher who is the lead author of the article. “And we also found that it is not restricted to stereotypical drug users with low socioeconomic status.”

After controlling for gender, education and income, the researchers found that professionals are equally as likely to use marijuana as those in other job classifications. Nearly 10 percent of the 35-year-old males with professional jobs report having used marijuana in the past month, for example.

Merline and co-authors Patrick O’Malley, John Schulenberg, Jerald Bachman and Lloyd Johnston, all psychologists at the ISR, discovered a high level of stability of substance use over the 18-year time period covered by the follow-up study. “The foundation for later substance use is set for most people by the time they finish high school,” Merline said.

The association between high school experience and cigarette smoking at age 35 is particularly strong, the researchers noted. Having even tried cigarettes at all before graduating from high school increases the odds of smoking at age 35 by more than 3 times the odds of those who had never tried cigarettes by their senior year.

The odds of smoking at age 35 were more than 12 times higher for participants who used cigarettes during the month prior to their twelfth grade survey than for those who had never smoked by their senior year. And the odds of smoking at age 35 were 42 times higher for those who were daily smokers during the twelfth grade than for those who had never smoked by their senior year.

Similar patterns were found for episodic heavy drinking, and for the use of marijuana and other illicit drugs. When compared with those who did not drink heavily as high-school seniors, participants who drank heavily had 3 times the odds of drinking heavily at 35 years of age. When compared with those who had not tried marijuana by the twelfth grade, individuals who had tried marijuana by the twelfth grade had 8 times the odds of using marijuana at age 35.

Those who had tried any illicit drug other than marijuana by their senior year had 5 times the odds of using cocaine and 3 times the odds of misusing prescription drugs at 35 years of age compared with those who had not.

But the researchers found that current demographic and socioeconomic factors also play an important role in adult substance use. Men and women who are currently married are much less likely to smoke, drink heavily, use marijuana or other illicit drugs or to misuse prescription medications than those who are single, divorced or separated.

While research on young adults has shown that college students drink more than their non-student peers while in college, by age 35 this pattern has reversed and college graduates are less likely to drink heavily than those who did not attend college.

The researchers also found that living with one’s child, rather than just being a parent, was associated with lower substance use. Still, they found that a sizeable segment of custodial parents drink heavily or use illicit substances. For example, more than 29 percent of fathers whose children live with them report heavy drinking within the past two weeks. Also, custodial parents are just as likely to smoke or misuse prescription drugs as those who have no children.

Established in 1948, the Institute for Social Research (ISR) is among the world’s oldest survey research organizations, and a world leader in the development and application of social science methodology. ISR conducts some of the most widely cited studies in the nation, including the Survey of Consumer Attitudes, the National Election Studies, the Monitoring the Future Study, the Panel Study of Income Dynamics, the Health and Retirement Study, the Columbia County Longitudinal Study and the National Survey of Black Americans. ISR researchers also collaborate with social scientists in more than 60 nations on the World Values Surveys and other projects, and the Institute has established formal ties with universities in Poland, China and South Africa. Visit the ISR Web site at www.isr.umich.edu for more information. ISR is also home to the Inter-University Consortium for Political and Social Research (ICPSR), the world’s largest computerized social science data archive.

A table is available at: http://www.umich.edu/news/index.html?Releases/2004/Jan04/merline

Web: www.isr.umich.edu