Cannabis contains various cannabinoids, two of which have almost opposing
actions: δ9-tetrahydrocannabinol (Δ9-THC) is psychotomimetic, whereas
cannabidiol (CBD) has antipsychotic effects. Hair samples were analysed to
examine levels of Δ9-THC and CBD in 140 individuals. Three clear groups
emerged: ‘THC only’, ‘THC+CBD’ and those with no cannabinoid in hair. The
THC only group showed higher levels of positive schizophrenia-like symptoms
compared with the no cannabinoid and THC+CBD groups, and higher levels of
delusions compared with the no cannabinoid group. This provides evidence of
the divergent properties of cannabinoids and has important implications for
research into the link between cannabis use and psychosis.