A new study reveals that marijuana abuse has a similar effect on dopamine response as other drugs and may increase depression and anxiety as a result. With the legalizing of recreational marijuana in some states and the medical use in many more, scientists are rushing to discover the long term effects of marijuana use. The results of this study show that prolonged practice may have a negative effect on mood and personality.
Researchers at the Brookhaven National Laboratory, New York University Langone Medical Center and the National Institute on Alcohol Abuse and Alcoholism completed a small study of the brain’s response to dopamine after prolonged marijuana exposure. It is well known that other drugs such as cocaine, heroin, nicotine, alcohol and methamphetamine mimic the release of dopamine into the brain. Dopamine is a neurotransmitter associated with feelings of pleasure, satisfaction and happiness. It is easy to see why people get addicted to drugs that can flood the brain with dopamine. Unfortunately, the body’s natural feedback mechanisms register the extra dopamine and the brain stops producing its own. In order to raise dopamine levels, more of the drug is necessary.
Previous studies, as a whole, have been inconclusive about marijuana’s effect on dopamine levels. Some early research determined that marijuana functions the same way as the other drugs but other research found that it did not. Tetrahydrocannabinol, THC, the psychoactive component in marijuana, seems to work more as an analgesic, reducing pain by altering neurotransmitters near the spinal cord. A user’s main response to the drug is relaxation and a decrease in aggression. It is also known to increase taste and appetite and has an effect on the visual, auditory and olfactory senses. Due to the way it operates in the body, cannabis has many medical applications. It can reduce pain and nausea for chemotherapy patients. It relieves pressure in the eyes of glaucoma patients, and it can alleviate pain and spasticity in multiple sclerosis patients. Now, a new study has shown that marijuana abuse may increase anxiety and depression via the decrease in dopamine experienced by the user.
Over the past few years moves have been made to decriminalize marijuana. California legalized medical marijuana in 1996 with Alaska, Washington and Oregon following two years later. Last week New York became the 23rd state to legalize marijuana for medical purposes. Colorado and Washington are the only two states to fully legalize marijuana, but other states are expected to follow. Many states have minimized the criminal charges for possession of marijuana. Will the trend continue as the new study reveals that marijuana abuse has a similar effect on dopamine response as other drugs?
A key word in the study is abuse. Joanne Fowler of the Brookhaven Institute and her colleagues examined the effects of steady, prolonged use of the drug. The experimental group consisted of 24 people who “had been smoking a median of about five joints a day, five days a week for 10 years.” When the drug methylphenidate was administered, the experimental group experienced a blunted dopamine response in comparison to the control group, 24 non-users. Methylphenidate, more commonly known as Ritalin, stimulates the production of dopamine in the brain. The experimental group did not feel “the cardiovascular, behavioral [or] brain changes usually associated with an increase in dopamine levels.” On the other hand, the control group had elevated blood pressures and altered moods. “Members of the control group reported feeling more high, restless, anxious and affected by the drug than the marijuana abusers did,” said researchers. PET scans confirmed greater physical changes in the brains of the control group.
Prolonged marijuana use blunted the response to dopamine in regular smokers. They did not feel the effects of the drug as strongly, nor did they derive as much pleasure from their other senses. The reward circuitry of their brains may have been disrupted by excessive use. Another sign that those who abuse marijuana have trouble experiencing pleasure, is a survey of their personalities. Marijuana abusers were more likely to have depression, anxiety, irritability and other negative emotions. It is not clear if this is due to marijuana’s effect on the user, or if negative moods were a pre-existing condition. Perhaps marijuana users are more prone to negative emotions and they self-medicate with THC, say experts.
On July 10, Arizona became the eighth state to authorize medical marijuana use for treatment of PTSD, Post-Traumatic Stress Disorder. Although studies have supported THC’s relief of symptoms because of its tendency to relax patients, researchers want to know if prolonged use of the drug may have the opposite effect. At first, marijuana enhances the senses to provide more pleasure; but long-term use may actually make it harder for people to feel happy and content.
Studies of marijuana use have been difficult due to its status as an illegal drug. Now a new study reveals that marijuana has a similar effect on dopamine response as other drugs and as a result of this action, abusers may experience an increase in depression and anxiety. This could be cause to look more carefully at a mood-altering substance that soon could be widely available for recreational use.
By: Rebecca Savastio