BDI scores did not statistically differentiate the two intervention groups until the final 8-week measurement point, when depression scores in the yoga group were significantly lower than in the control group. One interpretation of this finding is that there may be a delay in onset of yoga-specific mood benefit, perhaps related to the time involved for participants to learn and master the yoga exercises, and the time required for psycho-physiological factors mediating specific mood benefits of yoga to develop and exert a measureable effect. Such an interpretation is plausible given that other interventions for major depression have been associated with some delay in exerting specific, measureable mood effects. For example, pharmacological interventions for major depression often have a delay of 4 weeks before exertingsignificant mood effects over placebo, and may take 12 weeks to achieve full anti-depressant effects [140–143]. Aerobic exercise for major depression may have a delay of at least 4 weeks before exerting significant mood effects over a comparator, and may take 16 weeks to achieve full anti-depressant effects [144–147].