Marijuana users are more likely to experience negative emotions, particularly feeling alienated from others, new research reveals.
They are significantly more likely to feel that others wish them harm or are deceiving them, the 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 per cent of those aged 12 or over have used cannabis at some point in their lives.
How the research was carried out
The researchers, from the National Institute on Alcoholism and Alcohol Abuse in Bethesda, Maryland, analysed 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.