The 15q11.2 BP1–BP2 duplication has been reported to cause variable phenotypes including cognitive impairment, speech delay, and developmental delay (Burnside et al., 2011; Benitez-Burraco et al., 2017), as well as high inter-individual variability of neurodevelopmental disorders, such as schizophrenia (Kirov et al., 2012) and autism (Burnside et al., 2011). Here, IGFBP2 is linked to schizophrenia.