Intimate partners can have important influence on another's substance use: Study

A new study of young people in the two years after high school finds that those in romantic relationships are less likely than their peers to report heavy drinking and marijuana use.

Researchers have known that marriage lowers the odds that people will get drunk frequently or smoke pot, said study lead author Charles Fleming, a research scientist at the University of Washington. The new findings, he said, reveal that other kinds of romantic relationships have the same effect.

"I'm not saying that we should set up dating services," he said. "But it's something for parents to know and it's something for other people who are working with young adults of this age to know."

The study findings appear in the June issue of the Journal of Health and Social Behavior.

Fleming and colleagues examined surveys of 909 young people followed from first or second grade in the early 1990s through adolescence and the two years after high school.

More than 80 percent of the participants, from a school district outside Seattle, were white, and 54 percent were male.

The researchers found that those who were not in romantic relationships at ages 19 and 20 smoked less and drank less than other students back when they were in high school. The situation changed when they got older: "They catch up and maybe surpass their peers," Fleming said.

After adjusting their statistics so they would not be thrown off by factors like employment status, the researchers found the typical person who was not in a relationship was 40 percent more likely to use marijuana than a person in a dating relationship but without a live-in girlfriend or boyfriend.

What is going on? One possibility is that when people are in relationships, they are "happier and getting social support from their partner," Fleming said. "They're spending less time hanging out with their substance-using friends, spending less time at parties and in bars."

In the big picture, the findings matter because they provide insight into the influences on people during a time of life "when you see peak rates of alcohol abuse and development of dependency on cigarettes and marijuana," Fleming said. "You worry about people being disengaged from influences that might curb their risk of drinking and substance abuse."

Kenneth Leonard, a researcher with the Research Institute on Addictions at the University of Buffalo, said the findings add a couple new things to existing research. For one, they provide evidence that marriages among young people reduce the risk of substance use just as marriages of older people do.

But he said there is an exception: The study shows that when someone's spouse or boyfriend or girlfriend is a heavy drinker or marijuana user, that actually raises the odds that the person will smoke and drink.

Overall, the findings show that "intimate partners, even those who are cohabiting or dating, can have an important influence on another's substance use," he said.