Summary: Just one how of exercise a week can help to reduce depression risk, a new study reveals.
Source: University of New South Wales.
A landmark study led by the Black Dog Institute has revealed that regular exercise of any intensity can prevent future depression – and just one hour can help.
Published today in the American Journal of Psychiatry, the results show even small amounts of exercise can protect against depression, with mental health benefits seen regardless of age or gender.
In the largest and most extensive study of its kind, the analysis involved 33,908 Norwegian adults who had their levels of exercise and symptoms of depression and anxiety monitored 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 Associate Professor Samuel Harvey from Black Dog Institute and UNSW.
“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 – which was conducted between January 1984 and June 1997.
A healthy cohort of participants was 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. At 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 physical illness and perceived social support.
Results showed that people who reported doing no exercise at all at baseline had a 44% 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.
According to the Australian Health Survey, 20 percent of Australian adults do not undertake any regular physical activity, and more than a third spend less than 1.5 hours per week being physically active. At the same time, around 1 million Australians have depression, with one in five Australians aged 16-85 experiencing a mental illness in any year.
“Most of the mental health benefits of exercise are realised within the first hour undertaken each week,” said Associate Professor 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.”
The study involved researchers from Black Dog Institute, King’s College London, UNSW Sydney, Norwegian Institute of Public Health, University of Bergen (Norway), Nordland Hospital Trust (Norway) and the Arctic University of Norway.
The HUNT Study is a collaboration between the HUNT Research Centre, Norwegian University of Science and Technology, Norwegian Institute of Public Health and Nord-Trøndelag County Council.
Source: Gabrielle Dunlevy – University of New South Wales
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Original Research: Abstract for “Exercise and the Prevention of Depression: Results of the HUNT Cohort Study” by Samuel B. Harvey, F.R.A.N.Z.C.P., Ph.D., Simon Øverland, Ph.D., Stephani L. Hatch, Ph.D., Simon Wessely, F.R.C.Psych., M.D., Arnstein Mykletun, Ph.D., and Matthew Hotopf, F.R.C.Psych., Ph.D. in American Journal of Psychiatry. Published online October 3 2017 doi:10.1176/appi.ajp.2017.16111223
Exercise and the Prevention of Depression: Results of the HUNT Cohort Study
The purpose of the present study was to address 1) whether exercise provides protection against new-onset depression and anxiety and 2) if so, the intensity and amount of exercise required to gain protection and, lastly, 3) the mechanisms that underlie any association.
A “healthy” cohort of 33,908 adults, selected on the basis of having no symptoms of common mental disorder or limiting physical health conditions, was prospectively followed for 11 years. Validated measures of exercise, depression, anxiety, and a range of potential confounding and mediating factors were collected.
Undertaking regular leisure-time exercise was associated with reduced incidence of future depression but not anxiety. The majority of this protective effect occurred at low levels of exercise and was observed regardless of intensity. After adjustment for confounders, the population attributable fraction suggests that, assuming the relationship is causal, 12% of future cases of depression could have been prevented if all participants had engaged in at least 1 hour of physical activity each week. The social and physical health benefits of exercise explained a small proportion of the protective effect. Previously proposed biological mechanisms, such as alterations in parasympathetic vagal tone, did not appear to have a role in explaining the protection against depression.
Regular leisure-time exercise of any intensity provides protection against future depression but not anxiety. Relatively modest changes in population levels of exercise may have important public mental health benefits and prevent a substantial number of new cases of depression.
“Exercise and the Prevention of Depression: Results of the HUNT Cohort Study” by Samuel B. Harvey, F.R.A.N.Z.C.P., Ph.D., Simon Øverland, Ph.D., Stephani L. Hatch, Ph.D., Simon Wessely, F.R.C.Psych., M.D., Arnstein Mykletun, Ph.D., and Matthew Hotopf, F.R.C.Psych., Ph.D. in American Journal of Psychiatry. Published online October 3 2017 doi:10.1176/appi.ajp.2017.16111223