Early Cannabis Use and BDNF Gene Variant Increase Psychosis Risk

May 3, 2017 · Posted in Genetics, Risk Factors · Comment 

Teen smoking marijuanaNormal variations in genes can affect risk of mental illness. One gene that has been implicated in psychosis risk is known as BDNF. It controls production of brain-derived neurotrophic factor, a protein that protects neurons and is important for learning and memory. Another important gene is COMT, which controls production of the enzyme catechol-O-methyltransferase, which breaks down neurotransmitters such as dopamine in the brain.

Several forms of these genes appear in the population. These normal variations in genes are known as polymorphisms. Certain polymorphisms have been linked to disease risk. A study by Anna Mané and colleagues published in the Journal of Psychiatric Research in 2017 explored links between COMT and BDNF polymorphisms, cannabis use, and age at first episode of psychosis.

Mané and colleagues found that among 260 Caucasians being treated for a first episode of psychosis, the presence of a BDNF polymorphism known as val-66-met and a history of early cannabis use were associated with younger age at psychosis onset.

The val-66-met version of BDNF occurs in 25-35% of the population. It functions less efficiently than a version called val-66-val.

The researchers also found that males were more likely to have used cannabis at a young age.

Editor’s Note: In the general population, marijuana use doubles the risk of developing psychosis. Previous data had indicated that the risk was higher for those with a COMT polymorphism known as val-158-val that leads to more efficient metabolism of dopamine in the prefrontal cortex. The resulting deficits in dopamine increase vulnerability to psychosis compared to people with the val-158-met version of the COMT gene.

The new study by Mané and colleagues suggests that a common form of BDNF may be associated with an earlier onset of psychosis. Bottom line: Pot is dangerous for young users and can induce psychosis, particularly in people at genetic risk. Pot may be legal in many places, but heavy use in young people remains risky for mental health and cognitive functioning.

The company Genomind offers genetic testing for BDNF and COMT variants as part of a routine panel.

Cannabis Use May Cause Schizophrenia

May 1, 2017 · Posted in Risk Factors · Comment 

marijuanaCannabis use has been linked to schizophrenia risk, and new genetic research suggests a causal relationship between the two. In a 2017 article in the journal Molecular Psychiatry, researcher Julian Vaucher and colleagues reported that lifetime cannabis use was linked to schizophrenia even when the researchers controlled for 10 genotypes weakly associated with lifetime cannabis use. This makes it unlikely that the schizophrenia caused the cannabis use, suggesting instead that it is the cannabis use that leads to a schizophrenia diagnosis.

Vaucher and colleageus also controlled for genetic associations between cigarette smoking and cannabis use to eliminate cigarette use as a third variable causing the association between cannabis and schizophrenia.

The study by Vaucher and colleagues included 34,241 people with schizophrenia and 45,604 healthy controls.

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