Consistent with our findings, in another study with 83 inpatients with schizophrenia, schizoaffective or schizophreniform disorder with alcohol and drug abuse or dependence, global functioning in the substance use group was not worse than substance non-users (Dixon et al., 1991). Some evidence suggests that cannabis users may have higher functioning and paradoxically better outcomes, given the growing body of evidence on the endocannabinoid system in PD as well as some literature on the beneficial effects of cannabis. People with schizophrenia and cannabis use tend to have better cognitive function than non-substance users (D’Souza et al., 2005), which in part, explains better functioning. In a recently published study of 99 people with first psychotic episode, cannabis users had better cognition and social function at psychosis onset (Leeson et al., 2011). Cannabis users having better cognition may be due to the neuroprotective effect on the developing brain before the first psychotic episode. There is evidence from animal models that cannabis upregulates neurotrophins and enhances prefrontal neurotransmitter release (Jockers-Scherubl et al., 2007; Loberg & Hugdahl, 2009). Finally, continuous cannabis use after psychosis onset has been associated with a reduction in dysphoria and increased sociability (Dekker et al., 2009).
