IGFBP2 and Global developmental delay: However, cohort studies show that the 15q11.2 BP1-BP2 microdeletion is the most common genetic cause of ASD and schizophrenia [2, 10]; 15q11.2 BP1-BP2 is a susceptible region site for schizophrenia [11, 12] and developmental delay [13], and is associated with epilepsy [14, 15].