Researchers have warned that adolescents who are "internet addicts" may also be at increased risk of substance abuse.
Teens with "pathologic Internet use" are more likely to have past or recent use of illicit substances, said a study by Dr Georgios D. Floros of Aristotle University of Thessaloniki and colleagues.
The new research also points toward "some common personality characteristics" among adolescents who are abusing the Internet and have a history of substance use.
The researchers surveyed the entire adolescent population (aged 14 to 19) of the Greek island of Kos regarding Internet use, substance use, and personality factors.
Internet addiction means not just heavy Internet use, but also consequences such as losing track of time spent online, neglecting other activities, and having difficulty cutting down on Internet use.
Of the 1,221 teens who responded to the survey, about fifteen percent were heavy Internet users while five percent had signs of Internet addiction. Thirteen percent reported past substance abuse, including a seven percent rate of substance abuse within the past month. The researchers looked for possible links between Internet use and substance use, along with potential related factors.
As the severity of excessive Internet use increased, so did the likelihood of substance abuse. Males had higher rates of substance abuse than females.
Seeking online pornography was the only specific type of Internet activity that was more frequent among teens with recent substance use.
The relationship between Internet addiction and substance use remained significant, even after controlling for sex, age, ethnicity, and personality factors.
Especially since excessive Internet use that interferes with daily activities is readily observable at home, the results have implications for the early identification of teens at risk of substance abuse, Dr Floros and coauthors believe.
The study will appear in the March issue of Journal of Addiction Medicine, the official journal of the American Society of Addiction Medicine.