Critically, while the identification of 108 loci associated with schizophrenia was rightly heralded as a breakthrough in our understanding of the genetic determinants of schizophrenia, very little was made of this potentially vital insight. If smoking is indeed a causal risk factor for schizophrenia, then this has immediate and dramatic implications for public health, prevention, and treatment. Intriguingly, since the publication of these results, several other studies have been published that also support a causal role for smoking in schizophrenia and psychosis [28–31]. It is notable that one study reports a stratified analysis that suggests an association of CHRNA5-A3-B4 genotype with antipsychotic medication prescription (as a proxy of psychotic illness) in ever-smokers but not in never-smokers [32]. This is analogous to the case of CHRNA5-A3-B4 genotype and lung cancer risk, although the evidence in relation to schizophrenia is currently only suggestive.
