magazine issue 12 2006 / Issue 1

Does Exercise Truly Make You Happy?

• written by Daniëlle van Versendaal
• edited by Hans IJzerman

The effects of exercise are not observed immediately

More research is needed in order to confirm that exercise can truly counter depression. One of the goals is to establish a better understanding of the amount of exercise needed in order to see its effects. This is referred to as the dose-response relation in exercise treatment. Analyses of multiple studies (so called meta-analyses) have been conducted in order to determine the effective duration as well as the most effective type of exercise as an intervention. Many meta-analysis studies have encountered difficulties in comparing different results because the research designs differ remarkably. A good meta-analysis by Lawlor and Hopker (2001) selected 16 out of 72 relevant studies, including those with several exercise paradigms, several depression scales and designs with healthy and non-healthy subjects. Their findings were that several exercise paradigms had similar effects on depression. While other studies have found that for treatment of anxiety aerobic chronic exercise is more beneficial than non-aerobic exercise such as strength training (Petruzello, Landers Hatfiel, Kubitz, Salazer, 1991). Most meta reviews suggest that exercise programs are beneficial in depression after 4 to 6 weeks of intervention (Scully, Kremer, Meade, Graham, & Dudgeon, 1998). Unfortunately, only one of the studies reviewed by Lawlor and Hopker (2001) performed a follow up test of depression and found that the exercise intervention had no long-term effect.

In conclusion

In order to gain a more proper understanding of the causal relationship between exercise and depression (if any), one should examine several environmental and physiological mechanisms that are involved, as well as the use of random trials, drawn from the general population. For example, at the Vrije Universiteit in Amsterdam, a large study is now conducted in order to study the heritability of exercise behavior as well as the genetic factors involved with depression. A multidisciplinary study is unavoidable if we do not wish to be trapped into assuming that a correlation is the same as a causal relationship.

There is no reason to believe that exercise is not healthy of course. Do not let this article prevent you from going to the gym because of some scientific doubts on the psychological advantages (unless you were looking for an excuse to get out of exercising. By all means, stay home and relax). To answer the first question: does exercise make you happy? Not necessarily, and as an intervention for depression, surely it will not hurt. Just remember to stay critical, and most of all, inquisitive. Science still has a lot to unravel in our world and a lot of bright minds will have to put their heads together, for solving questions as these.

References

Cordain, L., Gotschall, R.W., Eaton, S.B. & Eaton, S.B. III. (1998). Physical activity, energy expenditure and fitness: An evolutionary perspective. International Journal of Sports Medicine, 19, 328-335.

Dishman, R.K. (1997). Brain monoamines, exercise, and behavioural stress: Animal models. Medicine and Science in Sports and Exercise, 29, 63-74.