COMT and schizophrenia: In one longitudinal study of a representative cohort followed from adolescence to adulthood, Caspi et al. [70] found that cannabis use in adolescence increased odds of schizophrenia and schizophreniform disorder in the catechol-O-methyltransferase (COMT) 158Val allele carriers, but not in the COMT 158Met allele homozygotes.