Cannabis users are more likely to experience negative emotions, particularly feeling alienated from others, new research reveals.

People who use marijuana are significantly more likely to feel that others wish them harm or are deceiving them, a US study found.

Brain scans also reveal the class-B drug increases signal connectivity in regions of the brain that have previously been linked to psychosis, the research adds, which is associated with severe depression.

Teenage cannabis users are particularly affected as their brains are still developing, according to the researchers.

In the US, 44 percent of those aged 12 or over have used cannabis at some point in their lives.

Cannabis users are more likely to experience negative emotions, particularly feeling alienated

GOING FROM BEING AN OCCASIONAL MARIJUANA USER TO INDULGING EVERY DAY RAISES A PERSON'S RISK OF PSYCHOSIS BY 159% Going from being an occasional marijuana user to indulging every day increases the risk of psychosis by up to 159 percent, research revealed last July. Marijuana is thought to cause psychosis-like experiences by increasing a user's risk of depression, a study found. The two mental health conditions have previously been linked. Frequently abusing the substance also significantly reduces a user's ability to resist socially unacceptable behavior when provoked, the research adds. Study author Josiane Bourque from the University of Montreal, said: 'Our findings confirm that becoming a more regular marijuana user during adolescence is, indeed, associated with a risk of psychotic symptoms. '[Psychosis symptoms] may be infrequent and thus not problematic for the adolescent, when these experiences are reported continuously, year after year, then there's an increased risk of a first psychotic episode or another psychiatric condition.' Advertisement

How the research was carried out

The researchers, from the National Institute on Alcoholism and Alcohol Abuse in Bethesda, Maryland, analyzed 60 people, half of which were cannabis dependent.

The study's participants completed a questionnaire that asked them about their feelings of stress, aggression, reactivity and alienation.

Brain scans were also taken of all of the participants.

Link between cannabis and mental health

Dr Cameron Carter, editor of the journal Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, where the study was published, said: 'These brain imaging data provide a link between changes in brain systems involved in reward and psychopathology and chronic cannabis abuse, suggesting a mechanism by which heavy use of this popular drug may lead to depression and other even more severe forms of mental illness.'

According to study author Dr Peter Manza, measuring brain activity is relatively easy and non-invasive.

Therefore, the procedure used in the investigation could be carried out to monitor cannabis users' mental health risks.

This comes after researchers from Warwick Medical School discovered in December last year teenage cannabis use may increase a person's risk of suffering from bipolar disorder in later life.

People who used cannabis at least two-to-three times a week at 17 years old are more likely to experience hypomania in their earlier 20s, according to the first study of its kind.