Exercise as it relates to Disease/Does exercise make you happy? The dose-response relation to exercise and reduction of depression symptoms

This is an analysis on the article "Exercise treatment for depression: Efficacy and dose response" by Andrea L.Dunn PhD, Madhukar H. Trivedi MD James B. Kampert PhD Camillia G.Clark PhD Heather O. Chambliss PhD.

Analysis by student u3161670.

Background to this research
Depression is a medical condition that significantly affects how an individual feels often causing a persistent lowering of mood. This can place great burden on how they function in everyday life. Exercise is commonly used in the prevention and treatment of a number of chronic diseases such as: Parkinson’s disease, multiple sclerosis, diabetes, hypertension, cardiovascular disease and many more. The study was conducted to test if exercise could be used as a treatment for someone with mild to moderate major depressive disorder and furthermore, the dose-response relationship of exercise and its reduction of depressive symptoms. With approximately only 23% of people seeking treatment due to the negative social stigma associated with this disease, it is thought by Andrea L. Dunn that perhaps if exercise was considered a viable treatment for mild to moderate major depressive disorder more people would seek treatment.

Where is the research from?
Lead researcher Andrea L. Dunn specialises in exercise science, health psychology, behavioural science and appears in numerous articles studying the effects of exercise on depression.

The research was conducted at:
 * Cooper Institute, Behavioural Science Research Centre, Golden, Colorado: Andrea L. Dunn PhD


 * University of Texas Southwestern Medical Centre, Depression and Anxiety Disorders Program, Dallas, Texas, USA: Madhukar H. Trivedi MD


 * Cooper Institute, Centres for Integrated Health Research, Dallas, Texas: James B. Kampert PhD, Heather O. Chambliss PhD
 * Alberta Children’s Hospital, Psychology Section, Calgary, Alberta, Canada: Camilla G. Clark PhD

What kind of Research was this?
The research was a randomised 2x2 factorial design plus placebo. This design allows researchers to test two interventions (energy expenditure and exercise frequency) and two levels of the intervention (low dosage, public health dose and 3, 5 days per week) in one study. The results can be measured against the placebo group to determine its effectiveness. Placebo group does not receive any of the interventions.

What did the research involve?
The research tests two interventions and two levels for each intervention on the reduction of depressive symptoms. The first intervention was exercise energy expenditure and the two levels were low dose (LD) which is expending 7kcal/kg/week and public health dose (PHD) which is expending 17.5 kcal/kg/week. The second intervention was exercise frequency and the two levels were 3 days per week and 5 days per week.

80 participants aged 20-45 diagnosed with mild to moderate major depressive disorder were randomly assigned to 5 possible groups: LD/3, LD/5, PHD/3, PHD/5 and placebo. The placebo group conducted 15-20 minutes of stretching 3 days per week. The placebo group is measured against the exercise groups to determine if there is a significant difference between exercise and basically no exercise in reducing depressive symptoms.

The 17- item Hamilton Rating Scale for Depression (HRSD17) was used to categorise the participants into mild or moderate severity and assess if the mean change in HRSD17 from baseline was greater in the exercise group compared to the placebo group. This is quite an old assessment measure and use to be the gold standard in assessment of depression but current research suggests that some aspects may be flawed and not as accurate as other tests. Perhaps a more reliable test could be used like the Patient Health Questionaire-9 (PHQ-9).

Participants took part in aerobic exercise on a treadmill or stationary bicycle under supervision in a lab to meet their required energy expenditure. There is no measurement of their energy expenditure outside the lab, this unknown information could be an implication for the test.

What were the basic results?
Over the 12 weeks there was a linear decline in HRSD17 scores for all groups, some more significant than others. The major finding was the significant response and remission rates from the public health dose groups. Response is defined as a 50% reduction in symptoms calculated from each individual’s baseline score. Remission is defined as a HRSD17 score of <7. The greatest response rate came from PHD/5 (44%) and the greatest remission rate came from the PHD/3 (41%) and an overall mean HRSD17 reduction of 47% from baseline. While there was some sort of benefit from the low dose groups, its effect was not much greater than the placebo group in fact, LD/5 had a lower response and remission rate compared to the placebo. Another finding was that there may not be a difference in frequency of exercise and the reduction of HRSD17 with only a 0.1 difference in declines of HRSD17 score between training 3 and 5 days a week (9.8 and 9.9). This suggests that response and remission of symptoms are based on total energy expenditure not frequency of training.

What conclusions can we take from this research?
Prescribing an energy expenditure dosage within the public health recommendations can be an effective intervention for treating mild to moderate major depressive disorder. Public health dosage has shown to have the best response and remission rates in this study whereas low dose exercise has little to no effect. There is research supporting the idea of exercise decreasing depressive symptoms; it suggests moderate intensity exercise for 150 minutes per week.

Practical Advice
Exercising within the public health guidelines, >30 minutes of moderate intensity at least 3 times a week can help reduce depression symptoms, in some cases it could be somewhat as effective as anti-depressants. Moderate intensity exercise is any activity that raises heart rate to 50-70% of its max, this can be exercises such as brisk walking, light jogging, bike riding and social games of cricket, tennis etc.

Further Readings
Helpful Websites

Lifeline Australia - 13 11 14 (Insert link) Beyond Blue – 1300 22 4636 (Insert link)

Journal Articles
 * 1) R E Sallis, (2009) Exercise is medicine and physicians need to prescribe it!. BMJ. 43(1).
 * 2) J Lepine, (2011) The increasing burden of depression. Neuropsychiatric Disease and Treatment. 7(1) 3-7
 * 3) D A Lawlor, (2001) The effectiveness of exercise as an intervention in the management of depression: systematic review and meta-regression analysis of randomised controlled trials. BMJ. 322(763).