New research has suggested that excessive use of the internet could lead to teenagers, who have no history of mental health problems, being at a heightened risk of developing depression.
More than 1,000 Chinese teenagers were involved in the study by scientists, led by Dr Lawrence Lam from the School of Medicine in Sydney, Australia, with an average age of 15.
Study participants were asked questions about their moods and anxiety, and whether they appeared to be linked with periods of being off-line.
A total of 2% of teenagers were classified as "severely at risk" at the beginning of the study, while 62 teenagers (6.2%) were engaging in "moderately" unhealthy internet use.
The teenagers were re-assessed after nine months, and the scientists found that 8.4% had developed clinical depression.
The authors of the study wrote in the journal Archives of Pediatrics & Adolescent Medicine: "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."
The scientists said that schools should consider screening children at school to identify teenagers suffering from depression and anxiety who might benefit from treatment.