2 Sources of Cannabis Addiction

Brain changes from using THC too frequently cause withdrawal and craving.

Posted Jun 15, 2020

Shakespeare coined the word addiction to mean “strong inclination” toward any activity. People continue using the word in this general way, e.g., “television addiction.” I use addiction in the more limited sense of drug-induced changes in the brain that alter experience and behavior to promote further use of the drug.

The experience of stopping frequent cannabis use is orders of magnitude less intense than stopping harder drugs such as alcohol, opiates or stimulants. No one is jonesing on the floor from running out of weed. On the other hand, quitting cannabis is more uncomfortable than quitting caffeine. The discomfort of nicotine withdrawal is the closest comparison to cannabis, though there are differences, particularly in the greater frequency of craving for tobacco. 

Cannabis causes two distinct changes in brain chemistry, physiology, and function that combine to create dependence. Its main psychoactive ingredient, THC, reduces the normal number of natural cannabinoid receptors, a process called downregulation. THC also alters reward circuitry, bending motivation toward continued cannabis use.

Downregulation of Cannabinoid Receptors

THC stimulates cannabinoid receptors (CB1) in the brain more strongly and longer than our natural cannabinoid chemistry. With CB1receptors activated far above normal physiological levels, most people enjoy physical relaxation, emotional calming, novel vivification of sensations, increased appetite (munchies) and ease falling asleep, among other changes to the texture of experience. As a result of THC’s strong activation, the brain reduces the availability of CB1 receptors in an effort to regain chemical balance.

When cannabis use is repeated before CB1 receptors upregulate back to normal levels, their reduction in numbers accumulates and lingers after THC’s high has ended. Normal levels of the natural cannabinoids anandamide and 2-AG do not have the normal number of CB1 receptors to activate This creates a relative cannabinoid deficiency state.

THC-induced cannabinoid deficiency state is the opposite of being high. Physical relaxation becomes restlessness. Emotional calm becomes anxiety and irritability. Munchies become decreased appetite. The novelty of sensations becomes boredom. Ease of sleeping becomes insomnia. These are withdrawal symptoms—the five signs of using cannabis too frequently.

Hijacked Reward Circuitry

Craving arises because THC alters brain reward circuity. All addictive drugs increase dopamine in the reward center - as much as ten times normal levels. Sex, exercise, and a good meal all naturally raise dopamine in the reward center, and this leads to repeating behaviors that promote survival. Unfortunately, the extreme rise in dopamine caused by alcohol, Xanax, opiates, meth, nicotine, caffeine and, yes, cannabis motivate repeating their use. After too frequent THC use has altered reward circuity by chronically flooding it with dopamine to the point of changing cellular structure, this portion of the brain starts crying out for repeat use when cannabis is stopped. 

A fascinating experiment reveals the impact of altered reward circuitry. When rats are given unlimited access to two water bottles, one sweetened with sugar and the other containing cocaine, they mostly drink the sugar water. Researchers define this as liking sugar water more than cocaine water. However, when rats are given access to only sugar water or only cocaine water and then the water supply is shut off, they return longer and more often to the cocaine bottle than to the sugar bottle. They work far harder to repeat cocaine water than sugar water. Researchers define this as wanting. Rats like sugar water more but want cocaine water more and work much harder to get it. Their heightened motivation toward cocaine is a sign of addiction.

Comparisons between humans and rats are more apt for some people than others, but all human and rat brains have natural cannabinoid chemistry operating within similar reward circuitry. I have heard many alcoholics, opiate and meth addicts say they don’t even like their drug anymore but can’t stop wanting it, often urgently. Reward circuitry controls wanting more than liking and this creates the experience of thinking obsessively about and desiring a drug, i.e., craving.

As THC bends reward circuitry toward itself, it diminishes motivation directed toward other rewards. This phenomenon was demonstrated by following a group of young adults for four years using a test of delayed monetary gratification and functional magnetic resonance imaging of their reward circuitry. A simple computer task earned the promise of monetary reward at the end of the task. Activity in the reward circuitry was measured during the anticipation of reward. Individuals who used cannabis most heavily showed decreasing activity in the reward circuitry over the four years. While this change could be interpreted as cannabis users gradually realizing the superficiality of greed for money, this would very possibly be mere rationalization. It makes more sense to interpret these results as a withdrawal of motivation for non-drug rewards due to THC-induced physical changes in the brain.


Cannabis addiction is real, Withdrawal discomfort from cannabis is far less intense than from most other drugs. However, when the discomfort of a cannabinoid deficiency state combines with increased motivation to use cannabis arising from hijacked reward circuitry, addiction results. The consequences of cannabis addiction are often subtle, but pervasive, and alter the trajectory of some people’s lives. Multiple cognitive, emotional, and psychological impacts have been observed and quantified by careful research Future posts will explore these impacts. 

The most obvious impact of withdrawal from cannabis is the difficulty many have continuing to abstain. Relapse stems both from unwillingness to tolerate the discomfort of withdrawal and from jumping to the conclusion that anxiety and insomnia are symptoms of underlying illness for which cannabis is the best medication rather than withdrawal from cannabis being the cause.

The bottom line is that adults can use cannabis safely and addiction is easy to avoid if you Know Your Limits. Everyone has their own brain and personality with their own unique limits. The five signs of using cannabis too frequently serve as useful guides to safe use when combined with the acknowledgment that cannabis addiction is real.