Is Cannabis as Safe as We Think?

By Thomas Schweinberg, PsyD, Staff Psychologist, Lindner Center of HOPE 








Over the last few years, cannabis has clearly become much more prevalent and accepted in this country, both for medical and recreational purposes. This is in stark contrast to the demonization of cannabis that existed from the 1950’s through the 1970’s. The pendulum has swung radically in the opposite direction as cannabis is now viewed as not only benign, but also a panacea for a multitude of ills. In fact, in the state of Ohio, as of the end of 2022, marijuana has been approved to treat 25 medical conditions. I am not aware of any other medication that is approved to treat over two dozen conditions. It would appear that cannabis is a very powerful medication capable of relieving many symptoms and conditions. Accordingly, shouldn’t we be asking what side effects we might experience from such a powerful substance? Yet, this information is not freely offered up as it is during every pharmaceutical commercial that we see on television. Instead, cannabis is generally portrayed as a substance with considerable upside and very little, if any, downside. Of course, this cannot accurately reflect reality.

Cannabis does have a number of benefits to its users, and I am actually in favor of its legalization. However, a great deal more needs to be done to inform and caution users about the potential side effects, some of which can be extremely disruptive, even life altering. Obviously, cannabis directly impacts the central nervous system when actively using, but what about over the long term? The National Institute of Health reported that chronic cannabis exposure, particularly during the period of brain development (up to 26 years old), “can cause long-term or possibly permanent adverse changes in the brain.” To begin with, animal studies have shown that exposure to cannabis is associated with structural and functional changes in the hippocampus, the brain structure responsible for consolidating and recalling new information, i.e., memory. Memory difficulties are likely experienced by the majority of those who use cannabis regularly, which is typically accompanied by poorer attention and slowed response time. What is less clear is how persistent these memory problems are after an individual stops using.

In addition to this, there is the potential for cannabis to globally impact a developing brain. As young brains develop, the connections between our brain cells, or neurons (via branch-like structures called “dendrites”) are either strengthened (because that connection is often used or adaptive), or they are pruned away (because that connection is seldom used or is maladaptive). Animal studies have revealed that exposure to cannabis during adolescence can provoke premature pruning of dendrites in the developing brain. The “before and after” images that come from these studies are very clear and compelling. While some of these neuronal connections may have eventually been pruned away anyway, it seems clear that some of these connections that are lost could have been strengthened and put to functional use during adulthood. This neurological impact may help to explain research findings which indicate that those who use cannabis chronically, particularly during adolescent brain development, are less likely to complete high school or obtain a college degree, have a lower income, experience greater unemployment, and report diminished life satisfaction. Certainly, this is not true for all who use, but those are the statistics.

Perhaps one of the most life-altering risks of using cannabis is the increased risk of experiencing psychosis that can become prolonged, or even life-long. There is considerable controversy about whether cannabis simply provokes psychotic symptoms in those who were already genetically predisposed to schizophrenia, or whether cannabis could cause a prolonged psychotic state which resembles schizophrenia. While the majority of users will not encounter psychotic symptoms, it does appear to be a sizeable minority, perhaps 10-15% of chronic users. Clinically, my colleagues and I have repeatedly seen the connection between cannabis misuse and psychotic disorders, enough that it is difficult to believe that it is merely coincidental. The association between cannabis and the onset of psychosis is great enough that the Canadian government has attached a warning label to its medicinal marijuana which reads, “Warning: Regular use of cannabis can increase the risk of psychosis and schizophrenia.” They added, “Young people are especially at risk.” Unfortunately, you will not find a comparable warning label in the United States.

While this article appears to generally denounce the use of cannabis, I should state again that I am in favor of its legalization as there are a number of potential benefits for those attempting to manage certain physical or emotional disorders. However, if cannabis is legalized without clearly reporting the potential side effects and adverse outcomes, we are being reckless and irresponsible. Those who produce and distribute legal cannabis should be held to the same standard as pharmaceutical companies who are compelled to advertise the potential risks of their products. While many or most who use cannabis can do so safely, there are those for whom cannabis presents a substantial risk for a number of cognitive and psychological difficulties. These potential risks should be clearly and responsibly communicated to the public as cannabis use becomes much more widely available. Otherwise, cannabis users could be misled into believing that its use is entirely safe and benign, unwittingly opening themselves up to possible long-term cognitive, psychological and functioning difficulties.

Continue to explore the relationship between cannabis and mental health