San Francisco  - Teenagers who watch a lot of television or spend long hours playing video games run a higher risk for depression as adults, according to a US study published this week in the Archives of General Psychiatry.

In the study, which began in 1995, 4,100 adolescents were asked about their television viewing habits and use of other electronic media such as video games. None of the participants had symptoms of depression when the study began.

But seven years later, 308 participants had developed symptoms consistent with depression, with those reporting more television use seeing significantly greater odds of developing depression, the study said.

"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 led by Brian Primack of the University of Pittsburgh School of Medicine.

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

While Primack noted that the study had not established a direct chain of causation, the relationship of increased viewing to depression indicated such a relationship.

According to Primack, television might promote depression because of its focus on bad news, traumatic events and negative role models. "You see a lot of depressing events on television and are likely to internalize them," Primack told US News and World Report.

TV viewing might also come at the expense of social, intellectual or sporting activities that help guard against depression, while late night viewing could disrupt sleep patterns that are important to healthy development, the study said. dpa