Investigators affiliated with the University of New Mexico assessed the effects of herbal cannabis inhalation on depressive feelings in 1,819 subjects over a one-month period. Study participants self-administered cannabis at home and reported symptom changes in real time on a mobile software application.
Researchers reported that “almost all patients in our sample [96 percent] experienced symptom relief from using cannabis to treat depression … with an average symptom intensity reduction of –3.76 points on a zero-to-ten visual analogue scale.”
Effects were generally limited in duration to two-hours or less. Cannabis varieties that were dominant in THC, not CBD, were most likely to be correlated with decreases in the intensity of depressive symptoms. Researchers reported “minimal evidence of serious side-effects in the short run,” though they acknowledged that prior studies have shown “mixed findings on the association between cannabis use and symptoms of depression, with unclear conclusions as to the direction of causality.”
They concluded: “Our results indicate that THC in particular is positively correlated with an immediate reduction in the intensity of depressive feelings. … Future research on cannabis and depression is needed, directly comparing the short- and long-term treatment effectiveness and side effect severity of cannabis use with conventional antidepressant treatment, in conjunction with conventional treatment approaches, and in the presence of clinically discouraged behaviors, such as alcohol consumption.”
Full text of the study, “The effectiveness of cannabis flower for immediate relief from symptoms of depression,” appears in the Yale Journal of Biology and Medicine.