Cannabis doesn’t kill brain cells like methamphetamine. Unlike alcohol, it doesn’t cause the connections between these cells to wither away. Instead—cue scary music—repeated cannabis consumption leads to a diminished effect better known as “tolerance.”
If you stop using cannabis, the brain can recover. And it does so impressively quickly, generally within weeks.
The reason for a consumer’s tolerance to THC can be explained by cannabinoid type I (CB1) receptors in the brain, which decrease with continued cannabis use. That is, you need to consume more of the high-inducing THC to get your buzz. Over time and with continued use, it may seem impossible to get high at all.
What Is “Tolerance”?
THC activates CB1 receptors to make you feel stoned. The high is essentially an abnormal increase in the activity of CB1 receptors. Once THC is gone, this activity usually returns to normal.
But if you repeatedly expose the brain to THC over a couple days or weeks, the brain takes action to minimize the increase in CB1 receptor activity; the brain fights back so that normal CB1 activation patterns are preserved. To do so, CB1 receptors are reduced, their effects weakened, or genetic expression altered. These mechanisms work to dampen the impact of THC so that in order to achieve the initial high, one must consume more. This is tolerance.
How Tolerance to THC Develops
THC causes tolerance through repeated activation of CB1 receptors. Repeated activation of CB1 receptors initiates events inside the brain cell that at first leads to desensitization, which is the weakening of the response to THC, followed by internalization, which is the removal of CB1 receptors from the cell’s surface. You’ll be able to detect when these processes occur because you’ll need to consume more THC to get high.
If you continue to consume THC, it will have less of an effect on brain functioning because there are fewer receptors for it to act on.
The difference between the two is that desensitized receptors are still available for THC to bind, but when it does bind, its impact is lower than it once was. Internalized receptors are no longer available for THC to bind since they’re brought into the brain cell from the surface where they stay or get broken down into smaller parts.
The activation of CB1 receptors by THC initiates these processes. As CB1 receptors get frequently activated, they become less associated with the components that carry out the receptors effects. CB1 receptors…