GSTM1 and thalassemia: As more data on this topic emerges, future analyses could include an adaptation of our model to examine the cognition and education effects on patients by Hb genotype (e.g., HbSS, Hb heterozygosity [HbSC], sickle-β0-thalassemia [HbSβ0], sickle-β+-thalassemia [HbSβ+], and hereditary persistence of fetal hemoglobin [HPHF]).