In contrast, when we used COT risk scores to predict schizophrenia diagnosis, we found that smaller P-values produced stronger signals (Table 2), indicating that genes most strongly associated with ND were associated with schizophrenia. The results imply that either ND and schizophrenia share some genetic liability, or ND is a risk factor of schizophrenia. These fit the predictions of the shared liability hypothesis and that smoking is a causal risk for schizophrenia. Of note, these two explanations are not mutually exclusive. But without data on smoking of the patients we are unable to test the latter possibility (e.g., by stratifying our sample on smoking status).
