Parents who are concerned that their teenaged child may be spending too much time on the Internet should now also be watching for signs of depression, according to a new study. The patterns of Internet addiction look similar to other pathological disorders, in which social and family relationships are sacrificed for the addiction, and academic and employment achievement suffers. Internet addicts, as a result, may also develop depression as they cut off ties from their social network and become more and more committed to time on the computer. The study was conducted in China, under the direction of lead researcher Lawrence Lam, who discovered that when teenagers spend excessive amounts of time on the Internet, they are one and a half times more likely to develop depression than teens that use the Internet more moderately. The study was published in the Archives of Pediatrics & Adolescent Medicine. Excessive use is described as spending at least five to ten or more hours per day on the Internet, says Lam, a psychologist at Sydney\u2019s University of Notre Dame\u2019s School of Medicine. Addicts often feel agitated when they are not using the Internet and can lose a desire for normal social interaction. The study recruited 1,041 teenagers between 13 and 18 years of age from the southern Chinese city of Guangzhou, they were not experiencing symptoms of depression when recruited. At the nine-month follow-up period 84 of the teenagers were diagnosed as suffering from depression and those who used the Internet at an excessive level were one-and-a-half times more likely to show depressive symptoms than those who used the Internet at a moderate level. The study\u2019s authors believe that the depression could be a direct result of excessive use of the Internet. Lam wrote, \u201cResults suggested that young people who are initially free of mental health problems but use the Internet pathologically could develop depression as a consequence.\u201d Lam co-authored the study with Zi-wen Peng at the Sun Yat-Sen University\u2019s School of Public Health, located in Guangzhou. The authors point to lack of sleep and stress from competitive online games as possible culprits for the cause of the depression. The study\u2019s findings are significant because it is the first study to investigate the pathological use of the Internet as a possible contribution to depressive symptoms. It may be beneficial, says Lam, to screen teenagers for Internet addiction to help them avoid developing depression as a result.