What's the science?

Current treatments for depression include medication and psychotherapy, however, these options can be expensive or show limited efficacy, and symptoms often persist. Resistance training has been associated with a reduction in anxiety symptoms. Although the physical benefits of resistance training are well understood, the mental benefits of resistance training have not been thoroughly investigated. This week in JAMA Psychiatry, Gordon and colleagues performed a meta-analysis of randomized clinical trials to assess the efficacy of resistance training in reducing depression symptoms.

How did they do it?

They included all randomized clinical trials in which participants were randomized to a resistance training intervention or to a non-active control group, and depression symptoms were assessed at baseline and mid and/or post-intervention. They accounted for other measures potentially related to depression such as age, sex, resistance training intensity, and trial duration and whether there was an increase in strength. They performed a meta-analysis, calculating the effect sizes for the association between depressive symptoms and resistance training for each study. They used a meta-regression (regression amongst all of the studies) in a moderator analysis which accounts for multiple moderator variables related to the effect of resistance training on depressive symptoms. There were four primary moderators of interest in the analysis: total volume of resistance training, health status, whether their assessment/allocation was blinded and whether there was an increase in strength.

What did they find?

They had a total of 33 clinical trials including 1877 participants that met their criteria for the analysis. They extracted 54 effects from these trials. Overall there was a significant moderate effect of resistance training on depressive symptoms (training reduced symptoms). This effect did not change dependent on the frequency, duration or volume of resistance training. In the moderator analysis they found that whether participants were healthy or physically or mentally ill, the total volume of resistance training or an increase in strength did not affect the reduction in depressive symptoms. Whether or not the participant was blinded to their outcome assessment had a significant effect on depression outcomes where effects on depressive outcomes were lower when the group allocation/depressive symptom assessments were blinded.