There has been a long debate over legalization, but is marijuana a good thing? Recent studies show that while certain chemicals in marijuana damage adolescent brains, they are beneficial to adults, especially those with diseases such as Alzheimer's.
Veronica Campbell, a neuropharmacologist from Trinity College in Dublin, says that marijuana truly works both ways.
A recent study conducted by Campbell and her team used the tetrahydrocannabinol ( THC ) chemical from marijuana-the chemical responsible for the high-and tested it on newborn, adolescent, and adult rats. In the newborn and developing adolescent rats, THC exposure resulted in brain cell death. In contrast, it was not as detrimental to neurons in adult rats.
Why does this happen? "We don't know," said Campbell in an interview with Scientific American Mind. "It's still being investigated."
"The most psychoactive cannabinoid chemical [in marijuana] is tetrahydrocannabinol," explains Dr. Jeffrey Henderson, director of Murine Imaging and Histology at U of T. "THC receptors in the brain are concentrated in the hippocampus ( the part of the brain associated with long-term memory ), amygdala ( associated with processing the memory of emotional reactions ), and the cerebellum ( associated with motor controls and sensory perception ), which are all affected when one gets high." Henderson points out, "the most clearly confirmed medical benefits of marijuana are anti-nausea, enhanced appetite, and pain decrease, [yet] long term usage may still be toxic to the brain."
Campbell's recent study highlighted the overall effects of THC on the human brain. The "slaughter" of young neurons by THC, as Campbell calls it, could explain why some who smoked pot while pregnant have children with cognitive impairment and why some adolescent marijuana users show brain damage in their still-developing neural circuits.
As neurons mature and cells age, their biochemistry also changes. Endocannabinoids ( the chemicals that regulate important functions in the brain, such as thought and perception ) start to shift and regulate different functions. These endocannabinoids appear to assist in the survival of neurons in adults. This is extremely important in patients with Alzheimer's disease, as it improves mental function by decreasing levels of the neurotransmitter acetylcholine, which contributes to memory loss. It also suppresses the toxic effects of the abeta protein, which kills brain cells.
Henderson explains, "THC acts by mimicking the actions of endocannabinoids, which normally exist in our brain. All of these agents work by suppressing a part of the normal inhibitory signals in our brains."
"While there is some evidence to suggest that THC derivatives may reduce Abeta aggregates in culture, a number of the mechanistic aspects of how this occurs are presently unclear. There is evidence to suggest that THC derivative competitively stalls the enzyme acetylcholinesterase, as well as prevents Abeta aggregation, a key pathological marker of Alzheimer's disease," says Henderson.
Before we start encouraging Alzheimer's patients to smoke up, Campbell told Scientific American Mind that "the beneficial effects of the THC are in much lower concentrations of the chemical that are found in the actual plant that people use to get high."
A new challenge is to isolate the important chemicals of cannabinoids in marijuana and see which ones, including the THC molecule, have a protective effect on neurons.
In small doses, there are some components of marijuana that when cultivated properly, could be potentially lifesaving. Overall, raw marijuana is still harmful when used over long periods of time.
Numerous studies are still being conducted in this area, so it looks like smoking a bowl isn't the answer quite yet.
November 16, 2009