Surprise: smoking pot dulls your motivation - study

And UK researchers say that's probably because the drug suppresses your ability to synthesize dopamine, the neurotransmitter associated with both pleasure and motivation.

In a small study, researchers from Imperial College London, University College London, and King's College London looked at the brains of 19 regular cannabis users who had been smoking pot since their teens.

The study's focus was on the controversial link between psychosis and cannabis, with all of the subjects having experienced psychosis-like behaviors when under the influence of the drug.

Using PET scans, the research team looked for differences in dopamine levels among regular pot smokers (at least once a week) against that of a control group, people who had smoked cannabis fewer than 10 times in their lifetimes and hadn't smoked at all three months prior to the study.

Abnormal dopamine activity is associated with psychotic symptoms, especially schizophrenia, reports Popular Science.

Findings showed that the regular, long-term pot smokers had the lowest dopamine levels, which the authors theorized could also contribute to one's lack of motivation after smoking pot. "Without the drive of dopamine, apathy reigns," writes Popular Science.