top candidates for ND related traits. But what we found was not the case. These top ranked candidates (i.e. those with P-values ≤ 5 × 10−5) from the PGC schizophrenia meta-analysis1 were not predict ND related traits. A likely explanation for these results is that genes most strongly associated with schizophrenia do not directly contribute to the smoking behaviors in schizophrenia patients. In other words, the reason why schizophrenia patients smoke is that they want to improve their cognitive functions and to suppress psychotic symptoms, not because that they are addicted to nicotine as regular smokers in the general population do. These results are consistent with the self-medication hypothesis.
