Researchers looked at the exposure to electronic media of 4,142 adolescents who were not depressed when the study began in 1995, before DVDs and the Internet were widely used.
The teens reported an average of 5.68 hours of media exposure per day, including 2.3 hours of television, 2.34 hours of radio, 0.62 hours of videocassettes and 0.41 hours of computer games.
Seven years later, when the participants were an average of 21.8 years old, 308 of them (7.4 percent) had developed symptoms consistent with 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 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," said the study, led by Brian Primack of the University of Pittsburgh School of Medicine.
Young women were found to be less likely to develop symptoms of depression than young men when exposed to the same amount of electronic media.
Depression, the leading cause of non-fatal disability worldwide, commonly begins in adolescence or young adulthood, the article explained.
The authors noted that time spent engaging with electronic media may replace time that could be spent on social, athletic or intellectual activities that could guard against depression.
Messages transmitted through electronic media may encourage aggression, inspire fear or anxiety and hamper identity development, they added.
Being exposed to media at night may also disrupt sleep important for emotional and cognitive development.
"When high amounts of television or total exposure are present, a broader assessment of the adolescent's psychosocial functioning may be appropriate, including screening for current depressive symptoms and for the presence of additional risk factors," the authors said.
"If no other immediate intervention is indicated, encouraging patients to participate in activities that promote a sense of mastery and social connection may promote the development of protective factors against depression."