Of the two general population-based studies of which we are aware, one showed that low IGF-1 in women, but high levels in men, were predictive of depressive disorder.37 In another, relative to moderate levels, women with high IGF-1 values experienced an elevated risk of minor depression.38 In both the studies, incident depression was rare resulting in low statistical power, and in one,38 the measurement of depression was made using a non-standard scale of unknown validity. This evidence concerns the gene IGF1 and depressive symptom measurement.