How Past Marijuana Use May Impact Personal injury Claims

By Roger Foisy on November 15th, 2018

Marijuana is the most commonly used drug in North America. Most marijuana users begin experimenting in adolescence, and according to the Canadian Centre on Substance Use and Addiction, over 25% of Canadian youth aged 15-24 use marijuana.1

With the recent legalization of cannabis for recreational use in Canada, I wanted to explore both how marijuana affects the brain and the impact that the past use of marijuana may have on personal injury claims.

How Marijuana Affects the Brain

Although cannabis flowers produce more than 100 types of chemical compounds known as cannabinoids, the two most common are:

  • THC (delta-9-tetrahydrocannabinol), the primary psychoactive component.
  • CBD(cannabidiol), which is not as psychoactive and is being studied primarily for medicinal applications.

When inhaled or ingested, these chemical compounds enter the blood stream and are carried towards the brain where they bind with cell receptors and change the ways in which cells communicate with each other. This in turn can trigger reactions in regions throughout the brain that influence memory, thinking, concentration, sense, perception, and coordination.

Scientific Studies: The Effects Marijuana May Have on Developing Brains

medical professional holding a human brainAccording to neuroscientific studies, our brains continue to develop through our early to mid-20s and are sensitive during this time to long-term or lasting harm that can be caused by substances like marijuana. For example, the frontal cortex (the area responsible for memory, judgement, and planning) is one of the last areas to develop and is therefore highly susceptible to permanent damage2:

  • 43 studies of chronic marijuana users found evidence of brain abnormalities and altered neural activity. After adolescents started to use marijuana structural and functional changes occurred rapidly, and users who started smoking marijuana before the age of 16 were more likely to be impulsive and more susceptible to addiction.3
  • In another study, neuroscientists used MRI to look for changes in the brains of individuals aged 18-25 who weren’t dependent but smoked at least once per week. Results showed brain changes that affected motivation, pleasure, and addiction, with participants who smoked more often showing more severe differences.

Scientists skeptical of these studies have argued that most fail to control for the use of alcohol and other societal factors. Others have proposed that genetics could have a greater impact on brain development than marijuana, while other research still has suggested cognitive changes may only be temporary unless used in dangerously high quantities from a very early age.4

Ultimately, while further study is needed into whether slightly frequent or infrequent use of marijuana among adolescents has significant long-term effects, the general consensus is that very frequent use of marijuana from an early age is likely detrimental to brain development.

Could Past Marijuana Use Impact Personal injury Claims?

In accident or injury cases, medical proof is crucial for determining what benefits an injured claimant is entitled to. When medical opinion is attributed to the accident, the claimant is generally entitled to benefits. If marijuana use from adolescence permanently or significantly impacted that person’s brain development, that information could be used to assess whether the injuries were caused by the accident or marijuana use. That result could have a significant effect on the benefits a long-term marijuana user receives if injured in an accident.

It is important emphasize that, as of today, it would be difficult to prove on a medical basis that a claimant’s past use of marijuana plays a significant role in brain development. That could change, however, as more in-depth research is conducted and new evidence emerges.

1 “Cannabis”, Canadian Centre on Substance Use and Addiction (August 2017).

2 Kristin Weir, “Marijuana and the Developing Brain”, American Psychological Association (November 2015).

3 ibid.

4 Hansa Bhargava, “Marijuana and the Developing Brain: Current State of Evidence” Medscape (20 April 2018)


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Roger Foisy

Roger Foisy

Roger R. Foisy is an experienced Ontario Personal Injury Lawyer helping accident victims and their families in Mississauga, Milton, Georgetown, Brampton, Oakville, and surrounding areas. Roger and his team dedicate a very personal level of attention to each and every client in their care and maximize clients’ personal injury settlements.
Roger Foisy