The stereotype of pot smokers as lackadaisical loafers is supported by new research: People who smoke marijuana regularly over long periods of time tend to produce less of a chemical in the brain that is linked to motivation, a new study finds.
Researchers in the United Kingdom scanned the brains of 19 regular marijuana users, and 19 nonusers of the same sex and age, using positron emission tomography (PET), which helps measure the distribution of chemicals throughout the brain.
They found that the long-term cannabis users tended to produce less dopamine, a “feel good” chemical in the brain that plays an important role in motivation and reward-driven behavior. [Trippy Tales: The History of 8 Hallucinogens]
Study participants who smoked marijuana regularly, and those who began using the drug at a younger age, had lower levels of dopamine in a part of the brain called the striatum, which could be why cannabis users appear to lack motivation.
However, “whether such a syndrome exists is controversial,” said study lead author Michael Bloomfield, a researcher at the Institute of Clinical Sciences at Imperial College London.
The people in the study used cannabis quite heavily, they all began using the drug between ages 12 and 18, and they all had experienced symptoms of psychosis while under the influence, the researchers said. Some of these symptoms include experiencing strange sensations while on the drug, or having bizarre thoughts, such as thinking they were being threatened by an unknown force.