Adolescents in the U.S., Canada and most countries in Europe are using less marijuana, perhaps because they also are socializing less, according to researchers who reviewed previously published prevalence studies from dozens of countries.

The Associated Press reported Feb. 2 that the review of data on more than 93,000 15-year-olds concluded that marijuana use declined in the U.S., Canada and in Western Europe between 2002 and 2006.

Researchers led by Emmanuel Kuntsche of the Swiss Institute for the Prevention of Alcohol and Drug Problems also found that the teens were spending less time going out with friends at night -- a finding they said could be related to the drug trend since youths who spend more nights away from home are more likely to smoke marijuana.

Kuntsche said that instant messaging, e-mail and cell phones "may have partly replaced face-to-face contacts, leading to fewer social contacts in the evening."

The research was published in the February 2009 issue of the Archives of Pediatrics and Adolescent Medicine.