Long Term Use of Cannabis Linked to Lack of Motivation to Work

A latest study published in the journal Biological Psychiatry states that long term use of cannabis lowers the level of dopamine in the brain linked to motivation.

The study conducted by the researchers at the Imperial College London, UCL, and King's College London, discovered that people who smoke cannabis have low levels of dopamine in the region of the brain called striatum. The same was noticed in those who started taking the drug at an early age. With this finding the researchers hope to explain why some cannabis users suffer from a lack of motivation to work or proceed with their normal interests.

Dr Michael Bloomfield, of Imperial College London, said, "Dopamine is involved in telling the brain when something exciting is about to happen - be it sex, drugs or rock 'n roll. Our findings explain why cannabis has a tendency to make people sit around doing nothing. The results weren't what we expected but tie in with previous research on addiction which has found substance abusers have altered dopamine systems."

With the help of PET scans (Positron Emission Tomography) they looked at the dopamine levels in the striatum of 38 people,  19 of these regularly used cannabis and 19 others were non cannabis users. All the 38 belonged to the same age and sex.

During the study, cannabis users experienced psychotic symptoms while smoking the drug such as strange sensations, peculiar thoughts and experiencing threat by an unknown force. The researchers expected the dopamine production to be higher in this group as higher levels of dopamine production have been associated with psychosis. But they were astonished to find a contradictory effect.

The participants in the study started having the drug between the ages 12 and 18 and due to having the drug early in life they had lower dopamine levels and the same was seen in those who smoked more cannabis. The researchers predict that cannabis use is the major reason for the difference in dopamine levels.

The lowest levels of dopamine were seen in those who met the diagnostic criteria for dependence of cannabis or cannabis abuse. They state that this measure could stand as a marker of addiction severity.

Prior to this, studies done have shown that cannabis users are at a high risk of mental illness and suffer repeated episodes of psychosis like schizophrenia.

"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," said Bloomfield. "It could also explain the 'amotivational syndrome' which has been described in cannabis users, but whether such a syndrome exists is controversial."