Marijuana has been used for recreational and medicinal purposes for centuries, evoking public interest and controversy along the way.

Xia Zhang, an associate professor in the University of Saskatchewan neuropsychiatry research unit, led the team that tested the effects of HU-210. The synthetic version is about 100 times as powerful as THC, the compound responsible for the high experienced by recreational users.

"This is a very potent cannabinoid oil," Zhang says. "It's not something that would be available on the street."

Learning and Memory

Rats treated with HU-210 on a regular basis showed neurogenesis -- the growth of new brain cells -- in the hippocampus, the researchers found. This region of the brain is associated with learning and memory, as well as anxiety and depression.

The effect is the opposite of alcohol, nicotine, heroin and cocaine.

"Most 'drugs of abuse' suppress neurogenesis," Zhang says. "Only marijuana promotes neurogenesis."

Depression may be sparked when too few new brain cells are grown in the hippocampus, scientists believe. It is unclear whether anxiety is part of this process but, if true, HU-210 could offer a treatment for both mood disorders by stimulating the growth of new brain cells.

Mixed Bag

Marijuana has been used for recreational and medicinal purposes for centuries, evoking public interest and controversy along the way.

As a medicine, the plant is used to ease pain in multiple sclerosis patients, combat nausea in cancer patients, and stimulate appetite in people afflicted with AIDS. It also has been used to treat epilepsy and stroke.

However, in addition to medical compounds, marijuana contains ingredients that may cause acute memory impairment, addiction and withdrawal, Zhang's earlier research suggests.