The drug’s pain-relieving properties make it a potential replacement for pain medication. In 2014, states that had legalized medical marijuana reported a 25 percent drop in deaths resulting from an overdose of pain medication.
In healthy people, marijuana is sometimes used as a substitute for other, stronger substances. Amanda Reiman, PhD, policy manager for the California office of the Drug Policy Alliance, and lecturer at the University of California Berkeley, shed light on this trend.
A 2009 study she conducted on medical marijuana users revealed that:
40 percent of them had substituted marijuana for alcohol
26 percent for other illicit drugs
66 percent for prescription drugs
Reasons they gave included:
marijuana had fewer unwanted side effects
it managed their symptoms better
it presented fewer problems with withdrawal
One marijuana user, Conrad, age 47, of San Francisco, said that when he can’t smoke, he drinks more.
“I’ve always found quitting marijuana to be easy when I needed to because of travel reasons or personal reasons, or professional, or what have you,” he told Healthline.
“I do know for certain that when I’ve been on vacation for a long time, and obviously I’m not smoking, I subconsciously substitute alcohol. I do drink more alcohol to ‘take the edge off.’”
Building up a tolerance
Dependence on marijuana happens when users build up a tolerance for the substance and need more and more of it to experience the same effect.
When a drug enters the brain, it overrides the brain’s natural processes, boosting a specific function far above, or below, normal levels.
The brain may become resistant to the effects of the drug in an effort to protect itself, so that next time the person uses the drug, it doesn’t have as strong an effect. In order to feel the same high, the person has to take larger and larger doses.
Over time, users may graduate from smoking marijuana to using it in high-dosage edible forms or propane-extracted concentrates called dabs.
A 2012 study found that people who use marijuana have fewer receptors in their brain for endogenous cannabinoids, the signaling molecules that marijuana’s active component, THC, mimics.
THC also affects the brain’s reward system and the release of the “pleasure hormone” dopamine.
“It is very well-known that dopamine is one of the most important neurotransmitters that regulates reward, motivation, and self-control,” said Dr. Nora Volkow, director of NIDA and one of the authors of the study.
“All of the drugs, whether legal or illegal, that can cause addiction apparently can stimulate dopamine signaling in the main pleasure center of the brain… By stimulating dopamine, they activate the main reward centers of the brain. This is why when someone takes a drug, it is pleasurable.”
Volkow also conducted a 2014 study that found that the brains of people who misuse marijuana have a decreased response to dopamine.
When given a chemical, methylphenidate, that caused dopamine levels to rise in the brain, the marijuana users didn’t respond as strongly or feel as high as nonusers.
And the more blunted their response to the methylphenidate, the more negative emotions they felt, including irritability, anxiety, depression, and aggressiveness.
“The problem isn’t that they are releasing less dopamine, but that the dopamine stimulation in the brain is having a very attenuated effect,” Volkow said.
“The brain doesn’t know what to do with the dopamine. The dopamine signal is not being heard, not communicating properly downstream.”
Volkow thinks that this decreased response to dopamine is likely caused by marijuana use. Another possibility is that marijuana users who become misusers have a dopamine system that’s naturally less responsive, making them more vulnerable to abusing the drug.
“The most common genetic legacy relating to addiction is inherited boredom,” explained Stalcup. “It’s a group of kids we call born bored. What they have scientifically is a pleasure system that’s about 20 percent below normal.
“When they first try a drug, like cannabis, the lights go on. They say ‘Doc, this is the way I’m supposed to feel. I’m so bored. But I don’t care if I’m bored when I’m high.’
“Here’s the bummer. It does benefit them. Their grades often will go up for a period of time. They’re more sociable. They do more things,” Stalcup added. “The tragedy is, they get tolerant.”
This explanation matches the experience that Gray, the writer for Vice, described.
“I smoke just to get through the boring parts of my day: grunt tasks like making breakfast, showering, running errands, and walking to work,” she wrote.
Her habit had increased from once to at least three times a day, smoking “between one and infinity joints at night, depending on how much weed I have.”
Volkow explained that the patterns of activity in the brain shift from the drug activating reward centers to activating other, nearby regions related to the formation of habits.
She said, “They start to recruit instead other [brain] networks that are associated with habits and routines. This allows a transition from a behavior that is predominantly driven initially because it’s pleasurable and rewarding to one that’s automatic because it creates a habit or routine.”