Study: Cannabis use does not increase dopamine release
By "Radical" Russ Belville on June 23, 2009
I have an acquaintence here in Portland who claims knowledge of "addictionology". When I have mentioned that marijuana use causes dependence in a few, not addiction, he's quick to correct me by saying that marijuana use causes the release of dopamine in the brain, just like any other addictive drug, and that is how we can consider marijuana to be physically addictive. I've always believed that correction to be faulty, but lacked the knowledge of brain functioning to offer a strong rebuttal.
Now it looks like I have a new study to back me up:
Background: Cannabis use in early adolescence may be a risk factor for development of schizophrenia. In animals, Delta9-tetrahydrocannabinol (THC) increases the rate of dopamine neuronal firing and release in the striatum. Thus cannabis use may increase dopamine release in the human striatum leading to vulnerability to psychosis
Aims: To investigate whether THC, the main psychoactive component of cannabis, can produce dopamine release in the human striatum.
Methods: 13 healthy volunteers, with previous cannabis experience, underwent two [11C]-raclopride positron emission tomography (PET) scans to indirectly measure striatal dopamine levels following either 10mg THC or placebo.
Results: Although THC markedly increased psychosis-like symptoms on the Psychotomimetic States Inventory (PSI), there was no significant effect of THC on [11C]-raclopride binding
Conclusion: In the largest study of its kind so far, we have shown that recreational cannabis users do not release significant amounts of dopamine from an oral THC dose equivalent to a standard cannabis cigarette. This result challenges current models of striatal dopamine release as the mechanism mediating cannabis as risk factor for schizophrenia.