Copy number variants (CNVs, defined as structural mutations that occur when genomic regions are duplicated or deleted compared to the reference genome which can be identified by chromosome microarray analysis) such as the 15q11.2 BP1-BP2 deletion may uniquely impact clinical phenotypes beyond simply increasing the risk for schizophrenia, thus potentially serving as models for studying treatment resistance in major mental illnesses [210,211]. The gene discussed is IGFBP2; the disease is schizophrenia.