Marijuana can increase dopamine, the brain’s pleasure and reward chemical.
You may have heard that marijuana has an effect on dopamine in the brain.
Dopamine is a brain chemical that makes you feel rewarded. It’s responsible for the pleasure you feel when eating, having sex, or using drugs.
This is because dopamine is found in the brain’s reward pathway. Many drugs stimulate this pathway, and marijuana is no exception.
In the short term, marijuana can increase dopamine activity. However, after regular and long term use, marijuana can decrease levels of dopamine. These effects are temporary, and users return to normal after quitting marijuana.
Let’s take a look at the connection between marijuana and dopamine.
What is Dopamine?
Dopamine is a brain chemical associated with pleasure and reward. Many biological functions involve dopamine, including appetite, attention, learning, sleep, sex, movement and mood.
The dopaminergic (dopamine-releasing) system is also associated with addiction. Most behaviours that are considered addictive activate the dopamine reward pathway, including drug use, food, gambling, and sex.
Many drugs of abuse, including cocaine, opioids, alcohol, and marijuana can increase dopamine levels in the brain.
Specifically, these drugs activate the area known as the reward pathway. When dopamine is released in this area, you feel good.
How Does Marijuana Affect Dopamine?
Marijuana increases dopamine in the brain in an indirect way.
The cannabinoids in marijuana do not act on dopamine neurons directly. Instead, they act on the endocannabinoid system. Cannabinoid receptors are found in many brain areas that have dopamine neurons.
Interestingly, dopamine neurons themselves don’t have any cannabinoid receptors. However, dopamine neurons in the reward pathway are inhibited by GABA neurons which do have cannabinoid receptors.
Here’s where it gets a little complicated. Marijuana activates CB1 receptors on GABA neurons, which inactivates them. What happens when you inhibit an inhibitor? The dopamine neurons become disinhibited, and more active.
What is interesting is that it’s not just chemicals in marijuana that have this effect. GABA is naturally inhibited by other cannabinoids produced by the brain.
The action of natural cannabinoids, known as endocannabinoids, is believed to play an essential role in the release of dopamine in day-to-day functions.
A study published in 2013 showed that mice born without cannabinoid receptors ran on their exercise wheels 20 to 30% less often than healthy mice.
The researchers concluded that the cannabinoid system may help facilitate dopamine release during exercise, and probably other reward-related functions as well.
Marijuana’s effects on dopamine are also thought to explain some of marijuana’s effects and side effects, including increased appetite, increased risk of psychosis, and cognitive and memory problems.
What Are The Effects On The Brain?
When marijuana is ingested, it increases dopamine in the reward pathway.
However, the link between marijuana and dopamine is not completely straightforward. Factors like tolerance, history of use, and strain content can all impact how marijuana affects dopamine.
THC seems to increase dopamine in the short term, while CBD does not.
A 1997 animal study found that THC stimulated dopamine neurons in the midbrain of rats. A 2016 study confirmed that marijuana increases the amount of dopamine in the midbrain reward pathway in humans, as well.
The effect of THC on dopamine explains why marijuana makes you feel good.
CBD, on the other hand, does not seem to impact dopamine. In a 1997 study, researchers found that CBD did not increase dopamine in reward pathways.
In a 2016 review, researchers concluded that low doses of THC increase the conversion of a precursor into dopamine, while high doses result in a decrease.
Regular marijuana use may cause a reduction in dopamine, but these effects are temporary.
A 1998 study found that long-term marijuana use reduced dopamine in the medial prefrontal cortex, an area of the brain associated with complex tasks like decision-making, memory, and planning.
The researchers believe a reduction in dopamine may be responsible for marijuana’s memory and cognitive impairments.
Long-term reductions in dopamine are also thought to play a role in marijuana withdrawal symptoms.
However, marijuana’s long term effects on dopamine seem to be temporary.
A 2012 study found that marijuana users who were abstinent for a period of time had normal levels of dopamine and receptors in the reward pathway of the brain.
By contrast, regular users of alcohol, heroin, cocaine, and amphetamine show abnormalities in these measures even after periods of abstinence.
Problems with Research
Researchers have been interested in marijuana’s effects on dopamine for a long time, because dopamine is known to be a target of drugs of abuse. Initial research took place in animals, but there is also some human evidence.
Unfortunately, some of the animal evidence has not corresponded with human results.
Whens studying long term use of marijuana, researchers often give animals marijuana for 3 weeks. On the other hand, human volunteers may use marijuana every day for years.
Researchers believe there are also genetic factors found only in humans that can impact the relationship between marijuana and dopamine.
As neuroimaging and other research techniques improve, scientists may be able to answer more questions about the link between marijuana and dopamine.
The link between marijuana and dopamine is complicated, but researchers have uncovered some basic facts.
In the short term, marijuana use tends to cause an increase in dopamine activity in the brain’s reward pathway. After long term use, dopamine levels may drop as the body downregulates these receptors. However, these effects are temporary and go away with abstinence.
Marijuana’s link to dopamine may explain some of marijuana’s side effects, including the risk for psychosis and cognitive problems.
Future research will reveal more about this fascinating connection.