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.”

Jan. 2012