To determine whether the initial finding in unrelated individuals was restricted to populations of Scandinavian origin, or more likely due to chance alone, we here analyse the relationship between MTHFR C677T polymorphism and age at onset in two additional samples of Icelandic and Danish patients with schizophrenia, and combine the results with the previous Scandinavian results in a meta analysis. The gene discussed is MTHFR; the disease is schizophrenia.