A seven year study, beginning in 1995, with researchers looking at exposure to media content, has shown an increase in the likelihood that young adults with a lot of media exposure are at a higher risk of depression.

4,142 teenagers in 1995 (who had no previous symptoms of depression) were monitored for the study. The then teens had reported an average of 5.68 hours of media exposure a day with a breakdown of 2.3 hours of television, 2.34 hours of radio, 0.62 hours of videocassettes and 0.41 hours of computer games.

In the now average aged 21 year olds, 7.4% (308) had developed symptoms of depression.

"In the fully adjusted models, participants had significantly greater odds of developing depression by follow-up for each hour of daily television viewed," wrote the authors of the study that was published in the Archives of General Psychiatry journal.

"In addition, those reporting higher total media exposure had significantly greater odds of developing depression for each additional hour of daily use," the study stated.

Young women were less likely to see depression symptoms than young men exposed to similar amounts of media content.

The researchers suggest that time spent engaging in TV time and playing video games can replace normal physical, social and intellectual activities that may guard against depression. Messages transmitted through electronic media may encourage aggression, inspire fear or anxiety and hamper identity development, they added, and that being exposed to media at night can disrupt sleep.