Using the Internet pathologically, to the point where the behavior resembles an addiction, might put teens at risk for depression, according to a new study.

The results show adolescents in China who used the Internet pathologically were 2.5 times more likely to be depressed after a nine-month period than those who did not exhibit Internet addiction.

Such extreme Internet use could be detrimental to adolescents' mental health, leading teens who are initially free of psychiatric problems to develop depression, the researchers say.

However, the researchers note that the link between Internet use and depression might not be a straight path. Rather, engaging in unreasonable and uncontrolled Internet use might lead to other pathological behaviors, which in turn could cause a downward spiral into depression, they say.

Also, the study was based on teens' own assessments of their Internet behavior and mental health, which could have influenced the results.

Assessing Internet addiction

Most studies that have examined teen Internet use and mental health have only looked at a "snapshot" in time. A study that followed teens over a longer period might be able to better distinguish whether mental health problems lead to pathological Internet use or whether the reverse occurs, the researchers figured.

In the current study, researchers surveyed 1,041 high-school students in China between the ages of 13 and 18.

The questions used to evaluate Internet addiction were based on those used to diagnose pathological gamblers and included: "How often do you feel depressed, moody, or nervous when you are off-line, which goes away once you are back on-line?;" "How often do your grades or school work suffer because of the amount of time you spend on-line?," and "How often do you choose to spend more time on-line over going out with others?" Students also answered mental-health questions.

Most students, around 94 percent, reported normal Internet use. About 6 percent, or 62 students, reported what is considered moderately pathological Internet use, and 0.2 percent, or two students, had severely pathological use.

Nine months later, the students again answered questions about their mental health.

There was an association between pathological Internet use in the first survey and depression in the second survey even after researchers took into account other factors that might influence the link, including age, gender, physical activity and dissatisfaction with their family life.

Preventing depression

Screening students for pathological Internet use in high schools might be a way to identify those at risk for mental health problems so they could receive counseling and treatment, the researchers say.

The study was conducted by Lawrence Lam of the University of Notre Dame, Fremantle, in Australia, and Zi-Wen Peng, of the School of Public Health, SunYat-Sen University, in Guangzhou, China.

The study was published online today and will appear will appear in the October print issue of Archives of Pediatrics & Adolescent Medicine, a Journal of the American Medical Association.