Depression

A great number of studies suggest that exercise training may reduce depressive symptoms in nonclinical and clin-ical populations (Blumenthal et al. 1989; DiLorenzo et al. 1999; Roth and Holmes 1987; King et al. 1993) and in patients with major depression (Blumenthal et al. 1999; Dunn et al. 2005; Singh et al. 2005; Martinsen et al. 1985; Klein et al. 1985; Veale et al. 1992; McNeil et al. 1991; Singh et al. 2001; Dimeo et al. 2001). In addition to meta-analytic results, selected studies on different aspects of exercise treatment of major depression are presented. Meta-analytic studies provide one means of summariz-ing the growing body of primary research and identifying variables that may moderate the effects of exercise on depression. North et al. (1990) analyzed 80 studies and reported an effect size (ES) of -0.53, indicating that exercise training reduced depression scores by approxi-mately one half a standard deviation as compared to the comparison groups; an even larger effect size (-0.94) was reported in clinical populations (e.g., substance abusers, post-myocardial infarction or hemodialysis patients). Including only studies with patients diagnosed with major depression (not due to a general medical condition, n = 30), Craft and Landers (1998) reported an effect size of -0.72, showing that only the length of the exercise program was a significant moderator of the clinical effects, with programs of at least 9 weeks being associated with larger reductions in depression. Patient characteristics (age, gender, severity of depression) were not significant mod-erators and when compared with standard treatment of depression (pharmacotherapy, psychotherapy), exercise training has comparable beneficial effects. Limiting the analyses to randomized controlled trials (n = 14), Lawlor and Hopkins reported an effects size of -1.1, when exer-cise training was compared to no-treatment control groups. In addition, exercise training was as effective as cognitive therapy, with a nonsignificant effects size of -0.3. Craft and Perna (2004) converted the overall effect sizes of these meta-analyses to a binomial effect size, allowing to examine the practical clinical significance: exercise train-ing increased the success rate to 67–74%. Because in a wide range of medical settings, a 50% reduction of symptoms is considered a treatment response, these success rates are quite remarkable. In a more recent quantitative and qualitative review of studies in patients diagnosed with major depression (n = 11), Stathopoulou et al. (2006) reported an effect size of -1.42 for the advantage of exercise training over control conditions. A possible dose response relationship of exercise in the treatment of major depression was studied by Dunn et al. (2005): a dose consistent with public health recommenda-tions (17.5 kcal/kg per week) (Pate et al. 1995) was an effective treatment for mild to moderate major depression and a lower dose was comparable to placebo with no dif-ferences between 3 and 5 weekly sessions. Although no control group was involved, a study of Dimeo et al. (2001) suggests that in treatment-resistant patients with major depression, 30 min of treadmill walk-ing for ten consecutive days may be sufficient to produce a clinically relevant and statistically significant reduction in depression, as measured with the Hamilton Depression rating Scale. These findings are substantiated by a more recent study involving a placebo exercise group (low-intensity stretching and relaxation exercises) in patients receiving a standard antidepressant treatment: the reduction of depression scores and the response rates were larger in the exercise training group Knubben et al. (2006). Some studies (Dunn et al. 1998; Kodis et al. 2001), but not all (King et al. 1991) have reported that supervised exercise training results in larger improvements in func-tional capacity compared with home-based exercise, and that greater energy expenditure is associated with larger reductions in depressive symptoms (Dunn et al. 2005). However, this issue needs further well controlled studies in patients with major depression. While most studies employed walking or jogging pro-grams, the efficacy of nonaerobic exercise has also been studied. In depressed elderly, a resistance training program was more effective than the control condition (Singh et al. 1997). Comparing random assignment to running or weight lifting, Doyne et al. (1987) reported that both the activities reduced depressive symptoms, and that there were no sta-tistically significant differences at the end of the active treatment phase or at follow-up after 1 year. Similarly, Martinsen et al. (1989) could not find differences between aerobic (jogging or brisk walking) and nonaerobic (strength training, coordination and flexibility training) exercise training. Blumenthal et al. (1999) could show that 16 weeks of group exercise training in older patients with major depression was as effective as antidepressant treatment with sertraline. Most remarkable is that, the 10-month relapse rate was significantly lower in the exercise group (8%), when compared to the sertraline (38%) or the com-bination group (31%) (Babyak et al. 2000). In a recent study, Blumenthal et al. (2007) reported that also in adults with major depression, the efficacy of exercise seems generally comparable to antidepressant medication and both tend to be better than placebo. Additionally, it seems that exercise compares quite favorably with standard psy-chotherapy of major depression: in the few studies that have evaluated their relative efficacy, running was just as effective as psychotherapy (Greist et al. 1979), cognitive therapy or a combination of cognitive therapy and running (Fremont and Craighead 1987