In popular imagination, marijuana users sometimes still tend to be stereotyped as lacking focus and as forgetful as goldfish. If you are older than 25, you will likely recall the infamously over-the-top “This is your brain on drugs” ad that compares a drug user’s brain to a frying egg. Another fine specimen of the genre features a habitually pot-smoking girl who is literally draped on the couch like some sort of deflated inner tube. At the time, anti-drug campaigners supported by National Institute on Drug Abuse and other governmental and non-governmental institutions wanted Americans to fear cannabis and place it in the same category of deadly substances as heroin and cocaine. Nowadays, with the mainstreaming of marijuana well underway, public opinion of cannabis has changed considerably, with the majority of U.S. states having granted legality to medical or recreational marijuana in one form or another. But for many people, the question still remains: what impact do cannabis and cannabis-derived medicines like CBD (cannabidiol) have on cognitive functioning? Is there a grain of truth to what we might call the frying-egg and deflated-inner-tube theory?
The answer is that it’s complicated. There are few studies of long-term cannabis use, and many of them do not test memory. The oft-repeated claim is that people who smoke a lot of weed starting young and continuing over a long period of time become cognitively impaired and carry a risk of psychosis and schizophrenia as well as an observable loss of short-term-memory functionality. This notion comes from a New Zealand study that has been criticized for not ruling out other social factors. These results are controversial and not universal. One trial of twins showed no difference in cognitive functioning between the twin who used marijuana and the one who did not, with researchers concluding the following:
There was no evidence of a dose–response relationship between frequency of use and intelligence quotient (IQ) change. Furthermore, marijuana-using twins failed to show significantly greater IQ decline relative to their abstinent siblings. Evidence from these two samples suggests that observed declines in measured IQ may not be a direct result of marijuana exposure but rather attributable to familial factors that underlie both marijuana initiation and low intellectual attainment.
The significance of this is potentially great. These findings throw something of a wrench into the conventional notion that marijuana use in adolescence permanently impairs the brain and leads to mental illness later on.
Yet another study, this one a yearlong study of 2000 British teens, after adjusting for other factors including cigarette smoking and social and mental health factors, made the following conclusion: “Modest cannabis use in teenagers may have less cognitive impact than epidemiological surveys of older cohorts have previously suggested.” This is potentially significant, as it challenges the claim that there is a direct causal relationship between teenage marijuana use and cognitive impairment.
Both of these studies suggest that when results include the important caveat of home, school, social factors, and mental health, the fried-egg crowd looks to have egg on its face.
One study showed that cognitive impairment caused by cannabis use (if it is present) may only be present when delta-tetrahydrocannabinol or THC (the psychoactive component of cannabis) interacts with cannabinoid type-1 CB1 receptors connected to the central nervous system. CBD, a non-psychoactive medicinal substance found in cannabis, does not interact with CB1 receptors in the central nervous system and instead interacts with CB2 receptors found in other kinds of cells, and CBD has never been shown to diminish cognitive functioning. In fact, CBD is a neuroprotective that may be able to help brain functioning.
Moreover, weed may be good for elderly brains: preclinical rodent trials show some evidence that THC could halt and even reverse some of the neural plaque buildup and brain inflammation of Alzheimer’s Disease (AD), with researchers observing that THC was actually more effective in halting the buildup of brain plaque than drugs currently on the market. Because of its interaction with central nervous system CB1 receptors, THC can work against Alzheimer’s Disease through multiple pathways. CBD is also promising because of its dual anti-inflammatory and neuroregenerative effects evidenced in preclinical trials.
For a long time, attention deficit disorder and attention deficit hyperactivity disorder (ADD/ADHD) patients have self-medicated with marijuana, and there has been anecdotal evidence that CBD can help people with ADD/ADHD to improve concentration. A 2016 German study found that patients who took whole-flower cannabis (see entourage effect) saw improvement in symptoms and concluded that cannabis may be an “effective and well-tolerated alternative” treatment for patients who do not benefit from standard ADD/ADHD medicines, which are often rife with side-effects.
Given all this evidence for the cognitive benefits of cannabinoids, we have come a long way from the “fried egg” view. As the body of evidence grows, we may reach a point where someone can make a more accurate “this is your brain on cannabis” commercial showing elderly people as they happily go about their lives and share easily recalled memories with loved ones. The same goes for the deflated, taciturn couch person of the anti-pot commercial, who with more evidence for cannabinoids’ medicinal qualities may have to give way to a well-adjusted social being, as CBD has been shown to have “considerable evidence as treatment for multiple anxiety disorders,” including social anxiety disorder (SAD).
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Cannabidiol (CBD) and Cannabis for Mental Focus and Acuity
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