RT Journal Article
SR Electronic
T1 Overlap between genetic variants associated with schizophrenia spectrum disorders and intelligence quotient: a systematic review
JF Journal of Psychiatry and Neuroscience
JO JPN
FD Canadian Medical Association
SP E393
OP E408
DO 10.1503/jpn.220026
VO 47
IS 6
A1 Nancy Murillo-García
A1 Sara Barrio-Martínez
A1 Esther Setién-Suero
A1 Jordi Soler
A1 Sergi Papiol
A1 Mar Fatjó-Vilas
A1 Rosa Ayesa-Arriola
YR 2022
UL http://jpn.ca/content/47/6/E393.abstract
AB Background: To study whether there is genetic overlap underlying the risk for schizophrenia spectrum disorders (SSDs) and low intelligence quotient (IQ), we reviewed and summarized the evidence on genetic variants associated with both traits.Methods: We performed this review in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and preregistered it in PROSPERO. We searched the Medline databases via PubMed, PsycInfo, Web of Science and Scopus. We included studies in adults with a diagnosis of SSD that explored genetic variants (single nucleotide polymorphisms [SNPs], copy number variants [CNVs], genomic insertions or genomic deletions), estimated IQ and studied the relationship between genetic variability and both traits (SSD and IQ). We synthesized the results and assessed risk of bias using the Quality of Genetic Association Studies (Q-Genie) tool.Results: Fifty-five studies met the inclusion criteria (45 case–control, 9 cross-sectional, 1 cohort), of which 55% reported significant associations for genetic variants involved in IQ and SSD. The SNPs more frequently explored through candidate gene studies were in COMT, DTNBP1, BDNF and TCF4. Through genome-wide association studies, 2 SNPs in CHD7 and GATAD2A were associated with IQ in patients with SSD. The studies on CNVs suggested significant associations between structural variants and low IQ in patients with SSD.Limitations: Overall, primary studies used heterogeneous IQ measurement tools and had small samples. Grey literature was not screened.Conclusion: Genetic overlap between SSD and IQ supports the neurodevelopmental hypothesis of schizophrenia. Most of the risk polymorphisms identified were in genes relevant to brain development, neural proliferation and differentiation, and synaptic plasticity.