Robert Turrisi of Pennsylvania State University in State College, Pa., said researchers mailed a handbook on how to have the conversation on alcohol to the parents of incoming freshmen.
Turrisi said timing counted. It had to be done before college; during college had no effect.
"By giving it to them during the summer before college, you not only could have a preventative effect at escalating to heavy drinking, but you can also reverse the effects of people that are heavy drinking," Turrisi said in a statement.
The study, published in the Journal of Studies on Alcohol and Drugs, suggested parents who talked to their kids about drinking before they went to college were more likely to have children who didn't drink after they arrived at college, and those who did drink drank less.
Turrisi advised parents to have a conversation, not a lecture about alcohol.