However, the relationship between schizophrenia and cannabis use may be more complicated than it initially seems. Despite a clear association between the two, the possibility of reverse causation has not been entirely excluded. Some small studies have suggested that it is in fact psychosis that is a risk factor for cannabis use, as those on a psychotic spectrum are more likely to experiment with drugs17, 18. The strongest evidence comes from Ferdinand et al. who found that the association was bidirectional, as cannabis naïve children with prodromal psychotic episodes had greater incidence of later cannabis use19. However, a similarly sized study failed to replicate this finding20. There is also possibility of attempts at self-medication, as it has been suggested that cannabis use can reduce negative and affective symptoms in patients with an established psychotic disorder21–23.
