The above figure shows that variations in a gene can affect the likelihood of developing psychosis in adulthood following exposure to cannabis in adolescence. The catechol- O -methyltransferase gene regulates an enzyme that breaks down dopamine, a brain chemical involved in schizophrenia. It comes in two forms: Met and Val. Individuals with one or two copies of the Val variant have a higher risk of developing schizophrenic-type disorders if they used cannabis during adolescence (dark bars). Those with only the Met variant were unaffected by cannabis use. These findings hint at the complexity of factors that contribute to comorbid conditions.