Cannabis Preserves the Aging Brain

The endocannabinoid system in the brain has been shown to have beneficial effects on cellular aging and memory.

These advantages are some of the latest findings on how Cannabis contributes to a healthy brain.

How has Cannabis functioned as medicine throughout history?

Cannabis as a medicine was known by the ancient Chinese. In 2737 B.C., the Chinese emperor Shen Nung (the Divine Farmer) referred to it as the "liberator of sin" and recommended it for the treatment of "feminine weakness," gout, rheumatism, malaria, constipation and absent-mindedness. By 1000 B.C., its medicinal use had spread to India and by 500 B.C., it was familiar to the ancient Greeks.

The earliest reference to the use of Cannabis as an inebriant was in 430 B.C., when the Greek historian Herodotus of Halicarnassus wrote about the Scythians burning the seeds and inhaling the smoke to induce intoxication during funerals.

The plant is also mentioned several times in the Old Testament as a bartering material, incense and an ingredient in holy anointing oil; it was likely used by the high priests of the temple, as well as by Jesus. At that time in history, the word messiah simply meant "the anointed one."

The use of the plant as an inebriant spread to the Muslim world and North Africa by 1000 A.D. and became endemic by the twelfth century.

The exploring Spaniards brought Cannabis to the New World in about 1545 AD.

A hundred years ago, the Smith brothers, William and Andrew - who became famous for the cough drop - investigated the use of Cannabis as a medicine. They found approximately fifty cannabinoid-based compounds, four being major cannabinoids: trans-delta-9-THC and delta-8-THC, cannabidiol (or CBD, the second-most abundant psychoactive ingredient after THC) and cannabinol or CBN, which may be a decomposition product of THC that accumulates as Cannabis samples age.

After ingestion, the trans-delta-9-THC is converted in the liver into 11-hydroxy THC, which is equally potent and psychoactive.

The leaves of the plant contain two to five percent THC. The flowers have up to twenty-five percent from their higher resin content. Concentrates such as hash oil have up to sixty percent. Modern methods of concentration have achieved levels of eighty to ninety percent THC by weight.

What does marijuana do in the brain?

It produces some excitatory behavioral changes, including euphoria, but it is not generally regarded as a stimulant. It can also produce some sedative effects, but not to the same extent as a barbiturate or alcohol.

Cannabis produces mild analgesic effects (pain relief), but this action is not related pharmacologically to the pain-relieving effects of opiates or aspirin.

Finally, marijuana produces hallucinations at high doses, but its structure does not resemble LSD or any other drug formally categorized as a hallucinogen. Thus, marijuana's effects on our body and brain are complex. So, how does it achieve these effects?

The very high potency and structure of the cannabinoids contained within the marijuana plant enable them to cross the blood-brain barrier and bind to a receptor for the brain's own endogenous cannabinoid neurotransmitter system. The two currently identified neurotransmitter compounds (there are probably more) in this system are anandamide, from the Sanskrit word ananda meaning "bliss," and 2-AG (2-arachidonoyl-glycerol).

Unlike the other neurotransmitters, these two endocannabinoids are not stored in synaptic vesicles. They are both produced within neurons and released to flow backward across the synapse to find their receptors, designated as CB₁ and CB₂. There are probably more of these cannabinoid receptors for marijuana in the human brain than for any other known neurotransmitter. The great abundance of these receptors and their widespread location gives an indication of the importance of the endocannabinoid system in the regulation of the brain's normal functioning.

What are some of the functions of endocannabinoids in the brain?

Anandamide inhibits the release of glutamate and acetylcholine within the cortex and hippocampus, an action that may underlie the ability of marijuana to impair one's capacity to form new memories when using the drug.

The presence of cannabinoid receptors in parts of the brain that control movement may explain the stumbling behavior that some marijuana users experience.

Cannabinoid receptors greatly enhance the release of dopamine; this action plays a critical role in the ability of marijuana to produce euphoria.

Finally, stimulation of cannabinoid receptors in the feeding centers of the hypothalamus may underlie the classic marijuana side effect known as the "munchies." Scientists began to investigate the use of cannabinoids as a diet aid for weight loss. Their hope was that producing a drug that blocked their action would produce an "anti-munchies" effect, thereby reducing food consumption and providing help to overweight patients.

Initially the drug scientists made worked fairly well. People reported being less attracted to eating. Unfortunately, they also became severely depressed. What this discovery tells scientists is that our endogenous cannabinoid system is normally involved, either directly or indirectly, in elevating or controlling our mood and that antagonizing the cannabinoid receptors in the brain, as had occurred with this novel drug, can produce some dangerous consequences.

How can Cannabis help the elderly?

In contrast, stimulating the brain's cannabinoid receptors may offer protection from the consequences of stroke, chronic pain and neural inflammation. Surprisingly, it may also protect against some aspects of age-associated memory loss. Ordinarily, we do not view marijuana as being good for our brain and certainly not for making memories. How could a drug that clearly impairs memory while people are under its influence protect their brains from the consequences of aging?

The answer likely has everything to do with the way that young and old brains function and the age-related changes in the actions of the neurotransmitters acetylcholine and glutamate. These two neurotransmitters are involved in making new memories and destroying old or unnecessary ones.

Early in life, this process of creation and destruction is in balance, and so interfering with it - which occurs when using marijuana - might impair memory. However, later in life, the roles of these neurotransmitters change in significant ways. In addition, the aged brain displays increasing evidence of inflammation and a dramatic decline in the production of new neurons, called neurogenesis.

Cannabis may offer protection in at least three different ways: by preventing the damaging actions of glutamate, by reducing brain inflammation and by restoring neurogenesis. Thus, later in life, pot might actually help your brain, rather than harm it.

The challenge for pharmacologists in the future will be to isolate the beneficial aspects of weed from its psychoactive effects, which themselves can be an additional burden to those suffering from the consequences of an aging brain.