Who should avoid using cannabis?

Cannabis has previously been classified in Canada and the United States as the worst type of drug – meaning it was completely illegal and had no recognized medical uses. For decades, this view persisted and set back research on the drug’s mechanisms and effects. Today, cannabis’ therapeutic benefits are widely acknowledged and some nations, including Canada, have completely legalized cannabis. But is it bad for your brain?

How does the endocannabinoid system work?

Cannabis acts on the body’s cannabinoid system, which has receptors all over the brain and body. Molecules native to the body, called endocannabinoids, also act on these receptors. We don’t totally understand the cannabinoid system yet, but it has one feature that provides a big clue to its function. 

Most neurotransmitters travel from one neuron onto the next through a synapse to propagate a message, but endocannabinoids travel in the opposite direction. When a message passes from from one neuron to the next, the receiving neuron releases endocannabinoids. Those endocannabinoids travel backward to influence the sending neuron – essentially giving it feedback from the receiving neuron. This leads scientists to believe that the endocannabinoid system serves primarily to modulate other kinds of signals – amplifying some and diminishing others. Feedback from endocannabinoids slows down rates of neural signalling. This doesn’t necessarily mean it slows down behaviour or perception, though. For example, slowing down a signal that inhibits smell could actually make smells more intense. 

How does someone get high?

When a person is smoking cannabis, one of the plant’s chemicals known as THC, passes from the lungs into the bloodstream. The THC is then carried by the blood to the brain, where it acts on specific cannabinoid receptors. These receptors are found in areas of the brain associated with: concentration, thinking, time perception, coordination, memory, and sensory pleasures. 

Should teenagers consume cannabis?

According to a 2018 survey in the US, 1 in 8 adolescents aged 12 to 17 had consumed cannabis within the last year. In 12th grade, about 1 in 16 consume cannabis daily. 

The brain’s response to counter the effects of THC impairs its attention, its ability to remember, and its potential for learning. These effects can last up to several days. This would not be such a problem if our brain ran like a machine, but that’s not the case. For teenagers’ brains, this problem is particularly pertinent as their brains are still developing.

What is the difference between teenager and adult brains?

In teenagers, the brain is still immature. It takes about 25 years for the human brain to be fully developed. This is why when teenagers and adults argue, they often come to different conclusions. Adults have a fully developed prefrontal cortex, the part of the brain that is responsible for judgment and an awareness of long-term consequences. The cortex of teenagers is still growing which means they are more easily influenced by their limbic system (the one that responds to fears and emotions). 

If teenagers consume cannabis, then their brain and the part responsible for controlling emotions may never reach its full potential. This can have long-term consequences and effects on one’s measurable intelligence, learning, and judgment. There is also evidence that some teenagers that use cannabis are at higher risk of developing depression or even a psychosis. 

Is there a negative relationship between cannabis and psychosis?

If you happen to be one of the people with a family history of psychosis, cannabis isn’t harmless at all. It hugely increases your chance of developing psychosis or psychosis-related symptoms. Because cannabis can have a direct effect on the structure of the brain, it can have this effect. Many people might also assume that they have no family history of psychosis, without realizing that they do. Because mental health issues have been so stigmatized historically, there is the chance that there is family history that one isn’t aware of. 

Can I smoke weed if I have bipolar disorder?

Many people who have bipolar disorder and also smoke cannabis have anecdotally stated that their symptoms improve significantly when they do not consume cannabis. This logically follows our understanding of how cannabis affects the brain more generally. People who have any issues with mental health and mental health management are more susceptible to the negative effects of cannabis, and so should be more careful when making the decision to consume.