Scientists link cannabis use with a damaging "shrinking" of certain parts of the brain, which is remarkeable for a number of reasons, not least of which as recent as 2005, scientists were hailing the benefits of cannabis, and its ability to repair damaged brain cells. Quite the connundrum?


A team of Canadian researchers reported that cannabis use appears to spur the development of new brain cells in rats and to have further beneficial anti-anxiety and anti-depressant effects.

While it has been known for more than 100 years that cannabis does no discernible damage to brain cells, only in the past ten years have reports demonstrated a direct neurological benefit.


The results support the anecdotal claims of thousands of patients, contradict decades of anti-marijuana propaganda used to prop up the foundering Drug War and suggests more social benefits to be had by legalizing cannabis for adults.

Because many social drugs, including opiates, alcohol, nicotine and cocaine, have been shown to suppress the formation of new brain cells when used chronically, cannabis had been suspected of doing so in a form of “guilt by association.” However, researchers in Israel found that cannabinoid drugs are helpful in cases of nerve damage and trauma. The US Department of Veteran Affairs found similar results working with veterans suffering from PTSD in the 1980s and suppressed the results.

Now, a team at the University of Saskatchewan department of psychiatry in Saskatoon, led by Xia Zhang, may have found evidence the drug promotes new brain cells to form in the hippocampus region of the brain, which reduces anxiety and depression.

Zhang and his colleagues wrote in the November issue of the Journal of Clinical Investigation that cannabis appears “to be the only illicit drug whose capacity to produce increased ... neurons is positively correlated with its (anti-anxiety) and anti-depressant-like effects.” The paper was posted online at the Journal’s website.

Rats in the study were injected twice per day for 10 days with HU210 -- a synthetic form of a cannabinoid found naturally in smoked cannabis. This is equivalent to “a high dose” of smoked cannabis, Zhang said, but given the variables of potency and cigarette size, he is not certain how many joints it would take for a human to match the dosage.