The second section of Table 2 lists three results that are, to the best of our knowledge, new both to genetics and epidemiology. One, we find a positive genetic correlation between anorexia nervosa and schizophrenia. Comorbidity between eating and psychotic disorders has not been thoroughly investigated in the psychiatric literature [43, 44], and this result raises the possibility of similarity between these classes of disease. Two, we estimate a negative genetic correlation between ulcerative colitis (UC) and childhood obesity. The relationship between premorbid BMI and ulcerative colitis is not well-understood; exploring this relationship may be a fruitful direction for further investigation. Three, we estimate a positive genetic correlation between autism spectrum disorder (ASD) and educational attainment (which has very high genetic correlation with IQ [37, 45, 46]). The ASD summary statistics were generated using a case-pseudocontrol study design, so this result cannot be explained by oversampling of ASD cases from the more highly educated parents, which is observed epidemiologically [47]. The distribution of IQ among individuals with ASD has lower mean than the general population, but with heavy tails [48]
