Cannabis

Question 0

MET v VAL

Answer 0

COMT codes for an enzyme that breaks down dopamine.
Enzyme has two forms: VAL and MET.
Inheriting 2 METs is not a problem: increases dopamine in prefrontal cortex an decreases it in midbrain.
Inheriting 2 VALs increases risk especially in adolescents who have smoked cannabis 3 times before the age of 15.
Increases dopamine activity in midbrain an decreases it in prefrontal cortex.

Question 1

Theory

Answer 1

Early use/heavy use produces an increased risk.
Dose effect but the effect is small (1.4%).
Cause or consequence.
Some people are more at risk: those with previous psychotic symptoms and those genetically at risk.

Question 2

Van Os et al 11

Answer 2

1900 people.
Followed for ten years and excluded anyone who had psychotic symptoms or had consumed cannabis previously.
Aged 14 - 24.
Measures cannabis use and psychotic symptoms at three points.
Controlled for SES, other drugs and other psychotic problems.
Cannabis significantly increased the risk of psychotic symptoms.
10 prospective studies supporting this.