Study Explains Why Marijuana Can Make Users Feel Paranoid
In the study, Steven Laviolette and his team at the University of Western Ontario in Canada trained rats to fear the scent of either almond or peppermint, by delivering a shock to their feet directly after exposure to the scent.
At the same time, the researchers also manipulated the activity of CB1 receptors in the brain. These cannabinoid receptors are activated by THC, the main psychoactive component of marijuana.
In some of the rats, researchers blocked CB1 receptor activity, and in others, they administered a marijuana-like drug to enhance it.
When the researchers blocked the CB1 receptors in the region of the brain called the basolateral amygdala, which is involved in processing fear and emotion, the rats that received strong electric shocks did not learn to fear the scent and continued to explore the cage and smell the scent, unaffected.
However, when the CB1 receptor activity was enhanced by the drug, even a minor shock was enough to make the rats freeze with fear when they were exposed to the scent again later. In comparison, control rats that did not have CB1 receptors blocked or enhanced did not learn to fear the minor shock.
The study results not only suggest that the basolateral amygdala is the region responsible for marijuana-induced paranoia, but also indicate that marijuana enhances a type of learning about fear.
The use of marijuana can lead the brain to jump to conclusions about mild experiences involving particular places or things and perceive them to be scarier and more strongly connected than they are – which can explain why users have an inclination to see patterns in events that aren’t real, such as conspiracies.
But researchers also found that this enhanced fear learning could be prevented when they activated the prefrontal cortex of the brain after administering the marijuana-like drug to the rats but before shocking them.
The prefrontal cortex is a higher-level brain area involved in planning, decision-making and controlling responses and impulses. For humans, this region may be activated by telling a person, “Calm down, you’re just high.”
These regions of the brain – the basolateral amygdala and the prefrontal cortex – are both believed to be involved in the pathology of schizophrenia, and researchers hope that understanding their interconnections may lead to better treatments for the disorder.
“We know there are abnormalities in both the amygdala and prefrontal cortex in patients who have schizophrenia, and we now know these same brain areas are critical to the effects of marijuana and other cannabinoid drugs on emotional processing,” Laviolette said in a statement.
The findings were published in the Journal of Neuroscience.