The Medical Research Council recently financed a study that was conducted by scientists at Imperial College London, UCL and King’s College London and published in the journal Biological Psychiatry that shows dopamine levels in a section of the brain called the striatum were lesser in individuals that use marijuana on a chronic basis and those who began using it at an early age.
The scientists are suggesting that this may be the reason that some recreational users appear to lack motivation to obtain gainful employment or pursue their normal interests.
PET brain imaging was used by researchers in the study to help determine dopamine production in the striatum of nineteen regular marijuana consumers and nineteen non-consumers of corresponding age and gender.
All the users in the study experienced psychoactive effects after smoking marijuana, some participants reporting strange sensations and others reported having bizarre thoughts like feeling as though they were being endangered by an unidentified energy.
The study’s researchers estimated that dopamine production could be greater in this group due to the fact that amplified dopamine production has been interrelated with psychosis, but they found just the opposite had occurred.
The participants in the study that use marijuana regularly reported having their first experience with the plant between the ages of twelve and eighteen years of age. There was a tendency for lesser levels of dopamine in users who started smoking marijuana at an early age, and for chronic consumers.
The researchers proclaim these discoveries propose that marijuana use may perhaps be the source of the difference in dopamine levels. The lowest levels overall were revealed in users that met analytical conditions for marijuana abuse or reliance.
The study’s leader, Dr. Michael Bloomfield from the Institute of Clinical Sciences at Imperial, shares his conclusions regarding the group’s findings for us below.
“It has been assumed that cannabis increases the risk of schizophrenia by inducing the same effects on the dopamine system that we see in schizophrenia, but this hasn’t been studied in active cannabis users until now.”
“The results weren’t what we expected, but they tie in with previous research on addiction, which has found that substance abusers — people who are dependent on cocaine or amphetamine, for example — have altered dopamine systems.”
“Although we only looked at cannabis users who have had psychotic-like experiences while using the drug, we think the findings would apply to cannabis users in general, since we didn’t see a stronger effect in the subjects who have more psychotic-like symptoms. This needs to be tested though.”
“It could also explain the ‘amotivational syndrome’ which has been described in cannabis users, but whether such a syndrome exists is controversial.”
Similar studies have examined dopamine release in former marijuana users without discovering differences in people who haven’t used marijuana, suggesting that the effects shown in this study are quite plausibly reversible.
For more information regarding the possible health risks related to chronic marijuana use see our correlated report on the possibility of chronic usage causing inflammation of the brain.