Bill Zimmerman, PhD, former President of Americans For Medical Rights, wrote in his 1998 book Is Marijuana The Right Medicine For You? A Factual Guide to Medical Uses of Marijuana:

“Using marijuana to treat mood disorders can be very tricky. Since active mood disorders often warp one’s observational skills, reports by patients about marijuana lifting them out of depression are inherently unreliable.

If you intend to use marijuana for this purpose, it is very important that you thoroughly discuss it with your doctor. Patients who respond well report that marijuana not only diminishes their undesirable moods, it also motivates them to productivity.

For some of these patients, depression was a by-product of a debilitating disease or illness for which marijuana provided a welcome remedy. For others, the marijuana seems to have acted directly on the depression.”