Is medical marijuana an effective treatment for depression, bipolar disorders, anxiety, and similar mood disorders?

PRO (yes) D. Mark Anderson, PhD, Assistant Professor of Economics at Montana State University, Daniel I. Rees, PhD, Professor of Economics at the University of Colorado Denver, and Joseph J. Sabia, PhD, Assistant Professor of Economics at San Diego State University, stated the following in their Jan. 2012 study "High on Life? Medical Marijuana Laws and Suicide," published by the The Institute for the Study of Labor (IZA) in its Discussion Paper Series: "Our results suggest that the legalization of medical marijuana is associated with a 5 percent decrease in the total suicide rate, an 11 percent decrease in the suicide rate of 20- through 29-year-old males, and a 9 percent decrease in the suicide rate of 30- through 39 year-old-males. Estimates for female suicide rates are generally measured with less precision and are sensitive to functional form... The strong association between alcohol consumption and suicide related outcomes found by previous researchers... raises the possibility that medical marijuana laws reduce the risk of suicide by decreasing alcohol consumption." PRO (NO) Gregory E. Simon, MD, MPH, Senior Scientific Investigator in the Center for Health Studies at the Group Health Cooperative, stated the following in a Jan. 2012 column titled "Ask the Doctor Q & A," published on the Depression and Bipolar Support Alliance website: "Using marijuana can certainly contribute to or worsen depression. Low motivation, fatigue, and withdrawal from positive activities are central features of depression and marijuana can worsen each of those problems. Some people do say that marijuana dulls anxiety or negative feelings. But it also dulls energy and motivation. And we know that activation and engagement are key parts of recovery from depression. Marijuana can be even more troublesome for people—especially younger people—who live with bipolar disorder. In addition to worsening depression, marijuana can increase the likelihood of experiencing symptoms of psychosis—like hallucinations or paranoid ideas. In younger people who are at higher risk for bipolar disorder or schizophrenia, using marijuana increases the chances of developing a severe or disabling mental illness."