Article by Josh Kaplan, Leafly
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.”
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.