THURSDAY, June 3 (HealthDay News) -- Young adults who are in a romantic relationship in the two years following high school are less likely to engage in heavy drinking or smoke marijuana, new research reveals.

The finding builds on past research that had demonstrated that marriage has a similar protective effect relative to drug and alcohol abuse.

"I'm not saying that we should set up dating services," study author Charles Fleming, a research scientist at the University of Washington, said in a news release. "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."

Fleming and his team report their findings in the June issue of the Journal of Health and Social Behavior.

The observation stems from a survey, initially launched in the early 1990s, which tracked more than 900 boys and girls beginning in the first or second grade through the two years after high school graduation.

The study authors found that while single 19- and 20-year-olds had actually smoked and drank less in high school than their peers, when they reached the cusp of young adulthood the consumption roles had reversed.

"They catch up and maybe surpass their peers," Fleming said, referring to the finding that at that age, single individuals were actually 40 percent more likely to smoke marijuana than those who still lived alone but were in relationships.

Fleming and his colleagues theorized that partner support might explain the finding, as well as the likelihood that those in relationships are happier and spend less time socializing among substance users in bars or at parties.

However, relationships did not always serve a protective function. The study also revealed that those in a relationship with a heavy drinker or marijuana user were, in fact, more likely -- not less -- to also smoke or drink.

More information

For more on substance abuse among teens and young adults, visit the U.S. National Institute on Drug Abuse.