Heavy and prolonged use of cannabis changes the release of dopamine in the striatum. This in turn has a negative impact on the cognitive functioning of the brain. Rubicon researcher Elsmarieke van de Giessen, who specialises in molecular psychiatry, has drawn this conclusion after a study on the long term effect of cannabis use. Lowered dopamine release was already proven with other addictive drugs, but not with cannabis use alone.
During earlier studies the research only focused on subjects who were addicted to multiple substances, most of which are already known for influencing the release of dopamine. Substances like: cocaine, heroine, nicotine and alcohol. Dopamine is an organic chemical in the brain that functions as a neurotransmitter – a chemical released by neurons (nerve cells) to send signals to other nerve cells. PET scans showed that an addiction to hard drugs like cocaine or heroine influences to dopamine system in the brain. The same effect with only cannabis wasn’t demonstrated until now.
It was quite a challenge to find sufficient subjects for the study since other addictions weren’t allowed. By using a system of measurement that’s really sensitive to dopamine release the study, on eleven subjects, was statistically strong enough. The eleven test subjects were tested positive for marihuana and had to stay clean in the hospital for a weak to be certain that the researchers weren’t just registering the direct effects of marihuana use. The test group ranged in the ages between 22 and 38 years old. On average, they had been heavy marihuana users for seven years.
Van de Giessen examined dopamine release in the striatum and surrounding areas in the brain by making PET scans with a tracer that binds to the dopamine receptors. The PET scans were made before and after a one-time amphetamine stimulation. The amphetamine stimulation has an immediate and accurately measurable effect on the dopamine system. It gives a good impression on the total dopamine release capacity of the brain.
The study concludes that among the group of long term cannabis users less dopamine is released in the striatum than among the control group. A relation was also made between a reduced release of dopamine in the striatum and impulsivity and depressive characteristics. The long term effect of cannabis use among addicts was more impulsivity and depression in comparison to the control group. The more impulsive and depressed the test subject were, the lower their dopamine release.
The study was done at Columbia University and New York State Psychiatric Institute. Elsmarieke van Giessen received a Rubicon grant back in 2011 from NOW. The grant is meant to give young Dutch researchers experience abroad.
(First picture source: www.consciouslifenews.com)