Blunt Truth: The Cognitive toll of Chronic Cannabis Use

Cannabis has been federally legal in Canada and is becoming legal in many states. Many people engage in using this substance recreationally. In Canada around 41% of individuals aged 16 to 19 reported using cannabis in the past 12 months. In the United States, 25.8% of 12th graders reported using cannabis within a similar timeframe. With Cannabis use becoming more and more discreet and easy to use with the use of devices such as vaporizers there is an increased risk of dependence and chronic long-term use among the youth who engage with this substance. While cannabis is often perceived as a benign recreational substance, accumulating evidence suggests that chronic or prolonged use may have significant neurological implications. This article dives into the current scientific understanding of these negative cognitive effects that result from chronic cannabis use, drawing upon reputable research studies to elucidate potential health hazards. 

One of the most concerning aspects of chronic cannabis use is its potential to impair cognitive functions. A study was conducted by Meier et al. (2012) which examined the association between persistent cannabis use and neurological decline. The researchers found that individuals who engaged in cannabis use heavily from adolescence into adulthood exhibited a significant decline in IQ and cognitive functioning compared to non-users. Most notably these deficits persisted even after participants ceased all use of cannabis. This would suggest that cannabis has long lasting effects on the brain. 

These findings underscore the vulnerability of the developing brain. The brain continues to mature until the age of mid-20s, early exposure to cannabis may interfere with critical neurological developmental processes, leading to irreversible consequences.

Beyond cognitive impairments, chronic cannabis use changes the structure of the brain. Gilman et al. (2014) used techniques to assess the structure of the brains of young adult cannabis users and discovered significant abnormalities in brain structures associated with motivation and reward, these structures are called the nucleus accumbens and the amygdala. 

Further, reductions in gray matter volume were observed, particularly in regions associated with memory and executive function; these regions are the hippocampus and prefrontal cortex. These structural changes of the brain may underlie some of the cognitive deficits observed in long-term users and may contribute to changes in behaviour and emotion. 

There is a complex relationship between cannabis use and mental health. Moore et al. (2007) conducted a comprehensive review and concluded that regular cannabis use increases the risk of developing psychological disorders such as schizophrenia. Most notably the risk of psychological disorders were significantly higher with individuals who have a family history of mental health conditions, this would suggest that genetics do play a factor. 

The mechanism behind this relationship is still unknown and is currently being investigated, but it is hypothesized that THC (The active compound in Cannabis) may alter dopamine (Pleasure compound secreted in the brain) regulation in the brain. Dopamine regulation plays a key role in psychological disorders. Once again this relation is still being investigated, however the strength of association, particularly in high-potency cannabis, warrants caution, especially for those with a family history of mental illness. 

Memory and learning are the most vulnerable to declination due to long term cannabis use. Schreiner and Dunn (2012) conducted a statistical review of multiple studies examining the residual effects of cannabis on cognitive performance. They found that long-term user consistently performed worse on tests of verbal memory and learning, even after extended periods not using cannabis. 

Specifically, for every five years of cannabis use, participants remembered fewer words from a standardized list. These findings are concerning, especially in academic contexts where memory and learning are critical for success. 

People often contradict the fact that cannabis is addictive, however evidence suggests that long-term use leads to dependence and withdrawal symptoms. A study by Lopez-Quintero et al. (2011) found that 1 in 10 cannabis users developed Cannabis Use Disorder (CUD).

Symptoms of CUD include compulsive use, unsuccessful attempts to quit, tolerance, and withdrawal. Common withdrawal  symptoms include irritability, poor sleep, decreased appetite and intense cravings. These withdrawal symptoms contradict the idea that cannabis is a low-risk substance and highlight the importance of awareness around its addictive potential. 

This body of research indicates that long-term cannabis use is associated with various adverse effects on brain health, including cognitive decline, structural brain changes and an increased chance of developing mental health disorders, memory deficits and potential for dependence. 

While societal perspectives of cannabis are evolving due to increased legalization, its is crucial to consider risks associated with chronic use. Individuals should weigh the benefits against the potential harms and make informed decisions regarding the use of the drug. Public health and policy also should incorporate these scientific findings so the public, especially adolescents, are aware of the risks of chronic cannabis exposure. 

References

Gilman, J. M., Kuster, J. K., Lee, S., Lee, M. J., Kim, B. W., Makris, N., Kouwe, A. van der, Blood, A. J., & Breiter, H. C. (2014, April 16). Cannabis use is quantitatively associated with nucleus accumbens and amygdala abnormalities in young adult recreational users. Journal of Neuroscience. https://www.jneurosci.org/content/34/16/5529 

Lopez-Quintero, C., Pérez de los Cobos, J., Hasin, D. S., Okuda, M., Wang, S., Grant, B. F., & Blanco, C. (2011, May 1). Probability and predictors of transition from first use to dependence on nicotine, alcohol, cannabis, and cocaine: Results of the National Epidemiologic Survey on alcohol and related conditions (NESARC). Drug and alcohol dependence. https://pmc.ncbi.nlm.nih.gov/articles/PMC3069146/ 

Schreiner, Dunn (n.d.). Residual effects of cannabis use on neurocognitive performance after prolonged abstinence: A meta-analysis. Experimental and clinical psychopharmacology. https://pubmed.ncbi.nlm.nih.gov/22731735/ 

Meier, M. (n.d.). Persistent cannabis users show neuropsychological decline from childhood to midlife | PNAS. https://www.pnas.org/doi/abs/10.1073/pnas.1206820109 

Moore TH;Zammit S;Lingford-Hughes A;Barnes TR;Jones PB;Burke M;Lewis G; (n.d.). Cannabis use and risk of psychotic or affective mental health outcomes: A systematic review. Lancet (London, England). https://pubmed.ncbi.nlm.nih.gov/17662880/   Assessed and Endorsed by the MedReport Medical Review Board