The primary psychoactive ingredient in marijuana is THC, tetrahydrocannabinol. Smoking or eating marijuana and its complex cocktail of compounds may rarely trigger episodes of depersonalisation, derealisation and psychosis. Sometimes it can induce paranoia, particularly in advocates of The War Against Drugs. More commonly, marijuana just leaves the user pleasantly and harmlessly stoned. It’s fun. Sleepiness, pain-relief and euphoria are typical responses. Cannabinoid CB(1) receptor agonists are potential antidepressants. Indeed cannabinoids may be neuroprotective against the effects of stress. Conversely, cannabinoid CB(1) receptor antagonists/inverse agonists, like the new EC-licensed diet-drug rimonabant (Acomplia), may cause depression and anxiety. Indeed the first brain-derived substance found to bind to our cannabis receptors was christened “anandamide”, a derivative of the Sanskrit word for internal contentment. Getting high may thus serve as an innocent recreational pastime in an uncaring world.
Yet marijuana is not a wonderdrug. Cognitive function in the user is often impaired, albeit moderately and reversibly. Marijuana interferes with memory-formation by disrupting long-term potentiation in the hippocampus. One of the functions of endogenous cannabinoids in the brain is to promote selective short-term amnesia. Forgetting is not, as one might have supposed, a purely passive process. Either way, choosing deliberately to ingest an amnestic agent for long periods is scarcely an ideal life-strategy. It’s especially flawed given the centrality of memory to human self-identity. Some artists and professional bohemians, it is true, apparently do find smoking grass an adjunct to creative thought. For persons of a more philistine temperament, on the other hand, it’s hard to see such a drug as a major tool for life-affirmation or the development of the human species. This shortcoming does not, one ought scarcely need to add, suggest marijuana users should be persecuted and criminalised. Indeed the marijuana compound THC may actually be superior to commercially licensed products at blocking the formation of mind-rotting amyloid plaques of the memory-destroying Alzheimer’s disease.