The study done in the University of California followed a procedure that included shooting capsaicin, the main ingredient for pepper spray, under the skins of 15 healthy subjects. The volunteers were then given doses of marijuana.
After 45 minutes, the subjects who smoked a moderate amount of marijuana described their pain to have subsided significantly. The subjects who smoked a lot, however, described their pain to be much worse.
McGill University's study included examining the effects of marijuana on the body's levels of serotonin, a substance that functions to regulate an individual's mood.
Done with lab rats as subjects, the study concluded that although moderate doses of marijuana increase serotonin levels, an excessive amount causes the levels to plummet - something that, according to McGill University's Dr. Gabriella Gobbi, has long been know to lead to depression.
This effect of marijuana is caused by the plant's chemical similarity to a natural substance known as "endo-cannabinoids", Gobbi explained. This substance, found in the brain, is released when a person is under conditions of high stress or pain, reports United Press International.
The study also reported excessive marijuana use in people suffering from depression significantly heightens the risks of psychosis.
