NEW YORK (Reuters) - Women who exercised frequently and didnt watch much TV were least likely be diagnosed with depression in a new study of middle-aged Americans. Researchers found that women who reported exercising the most in recent years were about 20 percent less likely to get depression than those who rarely got their blood moving. On the other hand, the more hours they spent watching TV each week, the more their risk of depression crept up - but the effect was smaller than it was for physical activity. The finding adds to the growing body of evidence that physical activity is important to maintain brain health, Dr. Gillian Mead, who studies geriatric medicine at Edinburghs Royal Infirmary but wasnt involved in the new research, told Reuters Health in an email. The study cant prove that watching too much TV and avoiding exercise causes depression. But more time spent off the couch and being active could boost self-esteem and womens sense of control, as well as endorphins in their blood, researchers wrote in the American Journal of Epidemiology. The report included close to 50,000 women who filled out surveys every couple of years as part of the US Nurses Health Study.