IGHE and major depressive disorder: Similarly, as one of the most abundant and most polymorphic trinucleotide repeats in the human genome, the AAT•ATT triplet repeats also show instabilities, which have recently implicated in some human health symptoms, for example, high IgE blood symptom in Chinese children [19], schizophrenia [20], [21], cocaine addiction [22], and prevalence of depression in Parkinson's disease patients [23].