A study posted on the website of the University of Michigan (UM) on Tuesday suggests that exercise and sleep impact depression differently in men and women. UM researchers looked at exercise and sleep patterns in more than 1,100 college students at Beijing University. Participants completed three questionnaires assessing depressive symptoms, physical activity habits and sleep patterns. Males in the study exercised more and at higher intensity than females, which helped protect against depression. For women, however, no level of physical activity significantly impacted depression. This contradicts general conclusions that regular physical activity helps reduce depression. The researchers also examined seven sleep variables, and found sleep was significantly associated with depression levels in both genders. On average, students reported quality sleep, but 16 percent of males and 22 percent of females reported poor sleep quality. Overall, students in the study did not report feelings of depression. However, more females, 43 percent, than males, 37 percent, reported depression. "This is consistent with existing research that higher rates of depression are found among women, with approximately a 2:1 ratio of diagnosis, although suicide rates are 3 to 5 times higher among men," said Principal investigator Weiyun Chen, an associate professor of kinesiology. The connection between sleep, exercise, and mood might also help explain females' higher rate of depression, Chen said. Depression and mood disorders are a serious problem in adolescents, with up to 20 percent of teens diagnosed with a mental, emotional or behavioral disorder. Roughly 1 in 7 college students is diagnosed with depression, with suicide the second-leading cause of death among them. Major depression involves symptoms persisting for at least two weeks, and can occur multiple times throughout life. Persistent depressive disorder, or dysthymia, is depression that lasts at least two years, and fluctuates in severity. Studies show that only about half of people with depression receive treatment. The study has been published online in the Journal of American College Health.