A new study led by Australian researchers suggests that regular exercise of any intensity can prevent future depression — and just one hour a week can help.
The landmark study by the Black Dog Institute reveals that even small amounts of exercise can protect against depression. Moreover, the mental health benefits are universal and extend to all ages and any gender.
The study appears in the American Journal of Psychiatry.
Researchers noted this is the largest and most extensive study of its kind, involving 33,908 Norwegian adults. Among the participants, investigators monitored levels of exercise and symptoms of depression and anxiety for over 11 years.
The international research team found that 12 percent of cases of depression could have been prevented if participants undertook just one hour of physical activity each week.
“We’ve known for some time that exercise has a role to play in treating symptoms of depression, but this is the first time we have been able to quantify the preventative potential of physical activity in terms of reducing future levels of depression,” said lead author Dr. Samuel Harvey from the University of New South Wales.
“These findings are exciting because they show that even relatively small amounts of exercise — from one hour per week — can deliver significant protection against depression.
“We are still trying to determine exactly why exercise can have this protective effect, but we believe it is from the combined impact of the various physical and social benefits of physical activity.
“These results highlight the great potential to integrate exercise into individual mental health plans and broader public health campaigns. If we can find ways to increase the population’s level of physical activity even by a small amount, then this is likely to bring substantial physical and mental health benefits.”
The findings follow the Black Dog Institute’s recent Exercise Your Mood campaign, which ran throughout September and encouraged Australians to improve their physical and mental wellbeing through exercise.
Researchers used data from the Health Study of Nord-Trøndelag County (HUNT study), one of the largest and most comprehensive population-based health surveys ever undertaken. The survey was conducted between January 1984 and June 1997.
Participants were asked at baseline to report the frequency of exercise they participated in and at what intensity: without becoming breathless or sweating, becoming breathless and sweating, or exhausting themselves.
During the follow-up stage, they completed a self-report questionnaire (the Hospital Anxiety and Depression Scale) to indicate any emerging anxiety or depression.
The research team also accounted for variables which might impact the association between exercise and common mental illness. These include socio-economic and demographic factors, substance use, body mass index, new onset of physical illness, and perceived social support.
Results showed that people who reported doing no exercise at all at baseline had a 44 percent increased chance of developing depression compared to those who were exercising one to two hours a week.
However, these benefits did not carry through to protecting against anxiety, with no association identified between level and intensity of exercise and the chances of developing the disorder.
“Most of the mental health benefits of exercise are realized within the first hour undertaken each week,” said Harvey.
“With sedentary lifestyles becoming the norm worldwide, and rates of depression growing, these results are particularly pertinent as they highlight that even small lifestyle changes can reap significant mental health benefits.”
Source: University of New South Wales