These are the most common concerns about cannabis side effects.
Photography by Georgia Love for Herb
We all know cannabis can have some borderline miraculous effects, treating everything from physical pain to PTSD. Yet, if we’re being honest, we’ll also admit that cannabis can have some undesired effects. The first step to fighting the hopelessly misinformed anti-drug messaging is to admit that cannabis isn’t totally harmless. But rather than attempting to bust some of the more outrageous claims out there – like those made by the Foundation for a Drug Free World which alleges that marijuana will make you a penniless, jobless, dickless, friendless, fuck-up – we’ve consulted the available research to give you an honest assessment of the potential side effects of cannabis.
Cannabis can certainly cause some people to feel anxious or paranoid, but for others like war veterans with PTSD, it’s been known to have a calming effect. So what gives? Why do some feel nervous when they smoke while others feel at peace?
THC, the main psychoactive component in cannabis, can have what is known as a biphasic response in those who consume it. Which is to say that small doses can have a calming effect while large doses can cause feelings of anxiety. When THC acts on the brain it affects a region called the amygdala. Since this is also the part of the brain which deals with our fight or flight reflexes, causing the amygdala to become too excited can result in the paranoid and anxious feelings.
In a study conducted on 42 volunteers at the University of Chicago, those who had taken a small dose of 7.5 milligrams of THC exhibited less anxiety during a mock interview than the volunteers who had taken a placebo, while those who had taken 12.5 milligrams of THC reported higher levels of stress.
Still, this doesn’t mean that everyone will react this way to a higher dose. In fact, studies on the effects of cannabis have shown that tolerance can increase with frequent use.
In many ways, the side effects of cannabis depend on the person consuming and their endocannabinoid system – the part of the body which is responsible for processing the many chemical compounds found in cannabis. Very little known about the way in which our endocannabinoid system works, though researchers have identified that cannabis receptors do exist in the human body. As a result, some have theorized that those who experience heightened levels of anxiety have cannabinoid receptors that are more easily stimulated than others.
Yet the placebo effect in each of these studies is an interesting window into how your personal biology and state of mind could affect your experience. In 2014 a study on cannabis and anxiety conducted by researchers at the University of Oxford, the Institute of Psychiatry at King’s College London, and the University of Manchester examined 121 individuals who had reported feelings of paranoia when they smoked.
Of those volunteers, one in five reported paranoid thoughts directly linked to their cannabis consumption, while 30 percent of the placebo group also reported having paranoid thoughts while consuming what they thought was THC. In fact, because of the double-blind nature of the study, volunteers who believed they were high had even fooled researchers.
Like many psychoactive substances, much of our experience can come down to our state of mind as well as our surroundings. This is something that psychedelic researchers refer to as set-and-setting. Put simply, psychoactive substances like cannabis can amplify whatever we may already be feeling and whether that feeling is comfort or panic can depend entirely on your personal biology and state of mind as much as it depends on the substance.
Short-term memory loss is perhaps one of the most iconic of cannabis symptoms. It’s been painted all over the puzzled faces of fictionalized stoners since the days of Cheech and Chong or at least as far back as we can remember. But does cannabis really cause memory loss, and if so, how severe is this herb-induced-amnesia?
In a study conducted at the University of Bordeaux in France, researcher Dr. Giovanni Marsicano found that specific neurons in the hippocampus, the part of the brain which is responsible for memory creation and retention, can be impaired by cannabis because it contains the necessary cannabinoid receptors to be affected by a cannabinoid compound. However, the study concluded that while cannabis could affect the brain’s ability to form memories, this is not the same as erasing previous memories or inducing a more serious form of amnesia.
In this way, cannabis is similar to alcohol, in that you can get so drunk that you black out. This has been reaffirmed by a 2013 study published in the journal Substance Abuse and Rehabilitation, which revealed that those who use cannabis on a regular basis have developed a tolerance to its memory-impairing effects and that memory loss is only present in someone who has just consumed cannabis, not afterward.
In essence, cannabis does make it easier to forget specific events that occurred when you were high, but you’re not likely to forget a childhood memory or anything else which happened before or after you’ve smoked.
The effects of cannabis on the heart are poorly researched. While we understand that cannabis affects our heart rate, much of the evidence today comes from self-reported cannabis use in people with a history of stroke or other heart problems. According to the New England Journal of Medicine, further studies need to be conducted on cannabis and its effects on the heart, but what researchers know as of now is that those who are at higher risk of heart attack and stroke may increase that risk by smoking. What is unclear is whether those effects are a direct result of cannabinoids or the act of inhaling the carcinogens released from a burnt substance.
Wherever you find someone who is opposed to legalization, a certain argument is sure to follow: ‘think of the children’ they say and some of these concerns are legitimate. After all, no one should be comfortable with openly encouraging the intoxication of children and that’s exactly why this argument against legalization is so powerful. But what are the real effects of cannabis use on an underdeveloped brain?
Several studies have shown that having a legal age of consumption may be a good idea. The reasoning behind this is that research has shown that the brain continues to grow and develop through to an individual’s young adulthood (at least until the age of 25). As a result, some health experts discourage the use of cannabis – and any other intoxicating substance – because of its potential to impede the brain’s development.
However, in a study published in the summer of 2018, researchers at the University of Pennsylvania found the claims that adolescent cannabis consumers may permanently damage the development of their brains by consuming cannabis may be overblown.
“Results indicate that previous studies of cannabis in youth may have overstated the magnitude and persistence of cognitive deficits associated with use,” the researchers write.
The study looked at data from more than 2,000 young cannabis users, which had been collected in previous studies dating back to 1973, and compared them to more than 6,000 volunteers who took part in their research.
In the immediate testing, those who consumed cannabis scored lower on the researcher’s tests than those who did not. But after 72 hours of sobriety, the volunteers returned to normal, suggesting that the long-term effects of cannabis use may not be as permanent as was previously thought.
Yet, as with everything else, more research needs to be conducted. In the future, we can look forward to more information from a 10-year study known as the Adolescent Brain Cognitive Development Study, currently being conducted at the National Institutes of Health which will monitor the health of more than 11,000 children over time to give a more complete picture of the effects of multiple substances.
Among the side effects of cannabis, the one which we know the least is cannabis’ impact on mental illness. Many cannabis patients swear by the plant as an antidepressant, a pick-me-up, and generally positive medicine.
In two recent studies conducted on the effects of cannabis on mental health in 2015 and 2016, psychologists discovered that cannabis has the potential to have a negative effect on mental health. But these studies also examined the effects of other factors like personal relationships and other stresses that can contribute to mental health or illness. They found that environmental factors were more accurate at predicting whether someone was at risk of developing mental health issues.
Those results were consistent with previous studies which found a link between frequent cannabis use and the risk of mental health issues, but also noted that cannabis may not be the direct cause.
Similar to anxiety, the effects of cannabis could be a trigger for something that is already present in the individual or in their environment rather than the root cause of the issue.