A study in the November issue of the British Journal of Psychiatry reports that participating in regular leisure-time physical activities of any intensity can lead to a decrease in depression. In a study of more than 40,000 Norwegian residents, investigators found that those who were not active during their time away from work were almost twice as likely to have symptoms of depression that those who were regularly active.

The investigators note that social benefits associated with exercise, such as increased number of friends and social support, may be more important contributors to this association than biological changes. However, there was no association found between workplace exertion (such as walking or heavy lifting) and decreased symptoms of depression.

Although many past studies have found lower rates of depression for people who are more active, "almost all of the published research on this topic has focused exclusively on intense leisure-time activity such as organized sports, jogging, and fitness classes," write the study authors. They note that results have been mixed when studies have considered other types of activities.

These participants (50.9% female; mean age, 45.9 years) were asked how often they engaged in light or intense physical activity during their leisure time and how active they were in their workplace. Light activity was defined as any activity not leading to being sweaty or out of breath.

They also underwent a physical examination and completed the Hospital Anxiety and Depression Scale questionnaire regarding symptoms of depression and anxiety. Social factors were also collected, including age, sex, marital status, education, social class, cigarette or alcohol use, any mental illnesses in immediate relatives, any somatic diseases, and level of social support.

Results showed that 10.1% had case-level symptoms of depression, 15.2% had symptoms of anxiety, and 5.6% had comorbid depression and anxiety. Those who participated in both light and intense leisure-time activities had decreasing rates of both depression and comorbid depression and anxiety symptoms based on amount of time spent on the activities.

In other words, "there was an inverse relationship between the amount of leisure-time physical activity and case-level symptoms of depression," investigators write. Although those who participated in light leisure activity had a slightly lower prevalence of anxiety, there was no association found with intense leisure-time activity. There were also no associations found between workplace activity and decreasing symptoms of any of the disorders studied.

However, the take-home message is that "we know from different sets of data that, at least for depression, some level of physical activity is helpful as opposed to not having activity." There is a large proportion of people who think exercise is too hard or that they do not have time for it. "For that population clinicians should be thinking about recommending that they should at least be engaging in the amount of physical activity that they think they're capable of. So again, little is better than nothing — which is actually a very good message.