Increased Prevalence of Rare Copy Number Variants in Treatment-Resistant Psychosis

BackgroundIt remains unknown why [~]30% of patients with psychotic disorders fail to respond to treatment. Previous genomic investigations into treatment-resistant psychosis have been inconclusive, but some evidence suggests a possible link between rare disease-associated copy number variants (CNVs) and worse clinical outcomes in schizophrenia. Here, we test whether schizophrenia-associated CNVs are more prevalent in patients with treatment-resistant psychotic symptoms compared to previously published schizophrenia cases not selected for treatment-resistance. MethodsCNVs were identified using chromosomal microarrays and exome sequencing in 509 patients with treatment-resistant psychosis (a lack of clinical response to [≥] 3 adequate antipsychotic medication trials over at least five years of psychiatric hospitalization). Prevalence of schizophrenia-associated CNVs in this sample was compared against a previous large schizophrenia cohort study. ResultsIn total, 47 cases (9.2%) carried at least one CNV with known or possible neuropsychiatric risk. The prevalence of schizophrenia-associated CNVs (n=21; 4.1%) was significantly increased compared to a previous schizophrenia cohort study (p = 0.005322; OR = 1.93). This increase in prevalence was primarily due to duplications at 15q11.2-q13.1 and 16p11.2, which were independently associated with treatment-resistance in pairwise loci-based analysis. ConclusionsThese findings suggest that rare schizophrenia-associated CNVs, particularly duplications of 15q11.2-q13.1 and 16p11.2, may serve as biological entry points for studying treatment resistance. Further investigation will be necessary to elucidate the spectrum of phenotypic characteristics observed in adult psychiatric patients with disease-associated CNVs.