(HealthDay)—People who exercise 2.5 to 7.5 hours a week have better mental health, but more than that is associated with poorer mental health, a new study suggests.
Researchers compared mental health to exercise by analyzing self-reported data from more than 7,600 adults who took part in a U.S. national survey.
"The largest mental health differences occurred with two to four hours of exercise per week. Beyond four hours, the trend begins to reverse: about 65 percent of those with poorer mental health exercised more than four hours per week, compared to 55 percent of adults in better mental health," wrote Dr. Yeon Soo Kim and colleagues at Teachers College, Columbia University.
They were surprised to find that after 7.5 hours of exercise per week, symptoms of depression and anxiety increased sharply. This was true in both men and women, and in people of all ages and different levels of health.
The study, published online and in the September issue of the journal Preventive Medicine, is the first to show an association between too much exercise and poor mental health, according to a Columbia news release.
However, further research is needed to determine whether people who tend to be depressed and anxious are more likely to be more physically active as a way to keep their mental symptoms under control, or whether greater amounts of exercise actually cause symptoms of depression and anxiety.
The researchers also emphasize that their findings support "the notion that regular activity may lead to prevention of mental health disorders."
"If physical activity can prevent mental health disorders or improve overall mental health, the public health impact of promoting physical activity could be enormous," they wrote in the study.
While the study found an association between high amounts of exercise and worse mental health, it did not prove a cause-and-effect relationship.
Explore further: Self-image and social interaction help to explain the link between exercise and mental health
The U.S. Centers for Disease Control and Prevention offers physical activity guidelines.