In yesterday's blog post, I gave some background to the SIGN guideline on non-pharmacological management of depression as well as details of how to download the draft guideline or see a webcast of the seminar where the draft guideline was presented.  On the day of the seminar itself, last Wednesday, after registration, coffee & initial orientating lectures, we moved on the first of four main treatment sections: "Lifestyle and Alternative/Complementary Therapies 1."

First off was Dr Ian Ross, a colleague I've known for many years, talking about the value of exercise as a treatment for depression.  Ian gave an impressive overview of this field with the concluding "grade A" recommendation that "Structured exercise is recommended as a treatment option for patients with mild to moderate depression."  SIGN's grade A recommendations are based on level 1++ or 1+ evidence (high quality meta-analyses, systematic reviews of RCTs, or RCTs with a very low or low risk of bias).  See the downloadable 34 page draft guideline for more on SIGN's levels of evidence, grades of recommendation, and good practice points.  The draft guideline states that "Exercise (both aerobic eg walking and jogging and anaerobic eg weight training) reduces depressive symptoms in patients with mild to moderate depression and is as effective as antidepressant medications.  This applies to interventions delivered in a variety of settings and in younger and older adults ... Drop-out rates were similar to medication trials (20-40%)."  The conclusions are similar to those I came to when reviewing the exercise and depression literature (much less rigorously) a few years ago (Hawkins 2005a).  I have a couple of points I would add.  One is encouraging - it now seems that anaerobic exercise can reduce mortality independently of changes in cardiorespiratory fitness (Ruiz, Sui et al. 2008), so it too (like aerobic exercise) has key general physical health benefits.  The other point makes me more cautious about painting too rosy a picture for the value of exercise in depression.  In twin studies from seven countries including the UK, it's been shown that genetic effects play a major role in determining exercise participation (Stubbe, Boomsma et al. 2006), at least for adults (Stubbe, Boomsma et al. 2005).  In their most recent paper entitled "Testing Causality in the Association Between Regular Exercise and Symptoms of Anxiety and Depression" (De Moor, Boomsma et al. 2008) these researchers reported on work involving 5,952 Dutch twins.  They stated "Cross-sectional and longitudinal associations (between exercise and measures of anxiety & depression) were small and were best explained by common genetic factors with opposite effects on exercise behavior and symptoms of anxiety and depression. In genetically identical twin pairs, the twin who exercised more did not display fewer anxious and depressive symptoms than the co-twin who exercised less. Longitudinal analyses showed that increases in exercise participation did not predict decreases in anxious and depressive symptoms. Conclusion: Regular exercise is associated with reduced anxious and depressive symptoms in the population at large, but the association is not because of causal effects of exercise."  I think it's important that SIGN have a look at this work before publishing the final depression guideline.  The randomized controlled intervention studies they have described (where exercise participation helps depression sufferers) are of central importance, but this work from twin studies needs to be taken into account too.

De Moor, M. H. M., D. I. Boomsma, et al. (2008). "Testing Causality in the Association Between Regular Exercise and Symptoms of Anxiety and Depression." Arch Gen Psychiatry 65(8): 897-905.  [Abstract/Full Text]
Hawkins, J. (2005a). "Alternative treatments for depression 1: exercise and 'wake' therapy." Journal of Holistic Healthcare 2(2): 9-15.  [Free Full Text]
Ruiz, J. R., X. Sui, et al. (2008). "Association between muscular strength and mortality in men: prospective cohort study." BMJ 337(jul01_2): a439-.   [Abstract/Free Full Text]
Stubbe, J. H., D. I. Boomsma, et al. (2005). "Sports participation during adolescence: a shift from environmental to genetic factors." Med Sci Sports Exerc 37(4): 563-70.  [PubMed]   
Stubbe, J. H., D. I. Boomsma, et al. (2006). "Genetic influences on exercise participation in 37,051 twin pairs from seven countries." PLoS ONE 1: e22.  [Abstract/Free Full Text]