Teenagers who are "addicted" to the Internet are more than twice as likely to become depressed than those who surf the Web in a more controlled manner, a study published Monday found.
For the study, published in the Archives of Pediatric and Adolescent Medicine, 1,041 teens from Guangzhou in southeastern China completed a questionnaire to identify whether they used the Internet in a pathological way, and were assessed for anxiety and depression.
The vast majority of the teens -- more than 940 -- used the Internet normally, but 62 (6.2 percent) were classified as being moderately pathological Internet users and two (0.2 percent) were "severely pathological" users.
Nine months later, the teens' psychological states were reassessed, and the researchers found that students who used the Internet uncontrollably or unreasonably were around two-and-a-half times as likely as normal Web users to develop depression.
Even when the stress of the teens' studies was factored into the equation, the Web-addicted teens were still one and a half times more likely to feel depressed at the nine-month follow-up than kids who used the Internet in a controlled way.
"This result suggests that young people who are initially free of mental health problems but use the Internet pathologically could develop depression as a consequence," study authors Lawrence Lam of the School of Medicine in Sydney, Australia, and Zi Wen-Peng of the Chinese Education Ministry said.
Pathological Internet use has been identified as a problematic behavior with signs and symptoms similar to those of other addictions, according to background information in the study.
Other studies have found that it is usually teenage boys who pathologically use the Internet, but the authors caution that the numbers of girls who show addictive Internet behavior is on the rise.
One warning sign of pathological Internet use: teens who were found in the study to be addicted to the Internet were more likely to use it for entertainment than for studying or gathering information, Lam and Zi found.
Then again, entertainment was the most common use of the Internet among the teens in the study, whose average age was 15.
The researchers suggest screening teens in their high schools to identify youngsters who are at-risk for becoming Internet addicts and possibly depressed because of their pathological behavior.