Study Explains why Marijuana use is Linked to Depression

A new study suggests that marijuana-use decreases brain's reaction to the neurotransmitter dopamine. The blunted response makes it difficult for marijuana abusers to feel pleasure.

According to Medline Plus, marijuana use can lead to memory, learning and behavior.

The current study was conducted by researchers at the Brookhaven National Laboratory, New York University Langone Medical Center and the National Institute on Alcohol Abuse and Alcoholism, according to MedicalXpress.

Researchers found that methylphenidate - a drug that stimulates dopamine production - did not cause any cardiovascular or brain changes in marijuana abusers. In people, who don't use cannabis, methylphenidate leads to high anxiety and increased heartbeat rate.

The study explains why marijuana affects the brain so differently than other drugs. Most drugs cause a release of the pleasure neurotransmitter called dopamine, which gives the users a high.

Other scientists are still unsure whether marijuana blunts the release of dopamine or not. A recent study had reported that long-term cannabis users produce less dopamine, which explains the lack of motivation and interest seen in these people.

In the present study, researchers gave 24 long-term marijuana users methylphenidate or Ritalin. The drug was also given to other healthy controls who didn't abuse marijuana.

Researchers found that controls experienced greater heartbeat rate and even high blood pressure. The same effect was missing in the test group.

Brain scans showed that certain brain regions in the test group were also smaller than in the control group.

Additional personality tests also revealed that marijuana abusers were more likely to be suffering from depression. Researchers aren't sure whether changes in brain lead to pot-smoking behavior or whether using marijuana causes the changes in the brain.

The research is published in the journal Proceedings of the National Academy of Sciences.