By Dr. Mercola
Regardless of your views on the pros and cons of recreational marijuana, the body of scientific evidence about its medicinal value is getting more compelling as additional research is done. The cannabinoids in cannabis — cannabidiol (CBD) and tetrahydrocannabinol (THC) — interact with your body by way of naturally-occurring cannabinoid receptors embedded in cell membranes throughout your body.
In fact, scientists now believe the endocannabinoid system may represent the most widespread receptor system in your body.1 There are cannabinoid receptors in your brain, lungs, liver, kidneys, immune system and more, and both the therapeutic and psychoactive properties of marijuana occur when a cannabinoid activates a cannabinoid receptor.
Your body actually makes its own cannabinoids, similar to those found in marijuana, albeit in much smaller quantities than you get from the plant. The fact that your body is replete with cannabinoid receptors, key to so many biological functions, is why there's such enormous medical potential for cannabis.
The whole plant also contains terpenes that have medicinal properties. More often than not, medicinal marijuana is made from plants bred to have high CBD and low THC content. While THC has psychoactive activity that can make you feel "stoned," CBD has no psychoactive properties. However, recent research shows THC should not be written off completely just because it's psychoactive. It has valuable therapeutic potential in its own right.
THC May Reverse Aging Process in the Brain
According to recent animal research,2 THC has a beneficial influence on the aging brain.3,4 Rather than dulling or impairing cognition, THC appears to reverse the aging process and improve mental processes, raising the possibility it might be useful for the treatment of dementia in the elderly.5
To test the hypothesis, mice were given a small daily dose of THC over the course of one month at the age of 2 months, 12 months and again at 18 months of age. It is important to understand that mice typically live until 2 years old. The dose was small enough to avoid any psychoactive effects.
Tests assessed the animals' learning, memory, orientation and recognition skills. Interestingly, 18-month-old mice given THC demonstrated cognitive skills equal to 2-month-old controls, while the placebo group suffered cognitive deterioration associated with normal aging.
According to one of the authors, neurobiology professor Andreas Zimmer, University of Bonn, "The treatment completely reversed the loss of performance in the old animals. We repeated these experiments many times. It's a very robust and profound effect." Even more remarkable, gene activity and the molecular profile in the brain tissue was that of much younger animals. Specifically, neurons in the hippocampus grew more synaptic spines — points of contact necessary for communication between neurons.
According to Zimmer, the THC appeared to have "turned back the molecular clock" in the THC-treated animals. (Previous research has also shown that the brain ages much faster in mice who do not have functional receptors for THC, suggesting THC may be involved in the regulation of the aging process.6) The team is now planning tests to see if the same holds true in human subjects.
Cannabinoids Maintain Homeostasis
Your endocannabinoid system has homeostatic properties, meaning it helps balance your body's response to stress. This helps explain some of the individual variations in response to cannabis.
In your brain, cannabinoids modulate neural activity. In younger people, in which endogenous cannabinoids are already plentiful, cannabis will not have the same effect as in older people, in whom activity of the endogenous cannabinoid system is much lower. The effects of THC in particular appear to vary significantly depending on age. As noted by Forbes:7
"[Y]ounger animals excelled at the tests when 'sober' but tended to struggle significantly under the influence of THC. 'Mature' and 'old' mice, on the other hand, struggled with tasks as consistent with their brain ages at first, but saw a huge increase in performance with THC infusions …
Overall, the results seem to support researchers' belief that the benefits for older mice are a result of stimulating the brain's endocannabinoid system, a biochemical pathway in both mice and human that grows less active over time."
In other words, in young mice (and probably people as well), THC can easily have an overly stimulating effect, resulting in a decline in memory and learning (albeit temporary, while under the influence). In older mice, a small amount of THC basically restored levels to a more youthful optimum.
Similarly, one of the reasons cannabis is so effective for seizures is because of this ability to regulate neuronal activity and reestablish homeostasis. If there's too much neuronal activity, the cannabis suppresses activity, and if activity is low, it raises it.