Figure 3. The bidirectional effects of SD differences in years of education and intelligence in UK Biobank.
The error bars indicate 95% confidence intervals around the estimated phenotype-SNP associations. Two sample multivariable Mendelian randomization using results from Hill et al. (2019), Okbay et al. (2016) and UK Biobank data. These results suggest that intelligence increases length of schooling and that higher education leads to higher intelligence. Pleiotropy robust methods, such as MR-Egger suggested little bias in the IVW estimates of the effect of intelligence on education, but that the IVW results may substantially overestimate the effect of education on intelligence. Estimates adjusted for month of birth, year of birth, sex, interaction of sex and year of birth and the first 40 principal components. For panel A, Q-stat = 368.7 (p<0.0001), I2gx=34.7%. For panel B, Q = 183.3 (p<0.0001), I2gx=12.5%.