Teens who sleep fewer than seven hours per night are more likely to use illegal drugs, according to a study released Sunday.
The research also found a link between a lack of sleep and the likelihood of illegal drug use, which can spread through teens' network "like a contagion," infecting siblings, friends and acquaintances as many as four degrees' separation removed.
Researchers at the University of California San Diego and Harvard University mapped the sleep patterns and drug use of more than 8,000 teens for the study.
"Adolescents are embedded in complex social networks and are especially vulnerable to peer effects -- possibly not only with respect to drugs, but also with respect to sleep," said the study, which was presented at the annual meeting of the American Association for the Advancement of Science.
The researchers found that a teen with one friend who sleeps fewer than seven hours is 11 percent more likely to sleep fewer than seven hours.
Teens with a friend who uses marijuana -- the most popular drug among US adolescents -- are more than twice as likely to use pot themselves.
The researchers also said that teens with a friend who sleeps less than seven hours per night are 19 percent more likely to use marijuana.
The study said the spread of poor sleep habits from one teen to another was partly to blame for an increased likelihood of drug use.
The research also suggested that a lack of sleep in induces teens to try alcohol, and said that increasing the number of hours a teen sleeps each night might help reduce substance abuse among adolescents.