Overview of genome-wide association studies related to IQ and schizophrenia
| Type of polymorphism | Study | Design | Country | Ancestry* | Participants, n | IQ measure | Mean IQ ± SD | Findings | ||
|---|---|---|---|---|---|---|---|---|---|---|
| Patients | Healthy controls | Patients | Healthy controls | |||||||
| SNP | LeBlanc et al. (88) (2012) | Case–control | Norway | European | 190 (SSD) | 353 | WASI | NA | NA | No significant association with IQ |
| SNP | Whitton et al. (89) (2016) | Case–control | Ireland | NA | 670 (SSD) | 330 | WTAR | 90.29 ± 18.08 | 119.81 ± 15.57 | rs6984242 (CHD7) and rs2905426 (GATAD2A) associated with IQ |
| CNV | Derks et al. (90) (2013) | Case–control | United Kingdom | Caucasian | 64 (schizophrenia) | NA | WAIS | NA | NA | 14 CNVs related to low IQ at chromosomes 15q11.2 and 22q11.21 |
| CNV | Martin et al. (91) (2014) | Case–control | Australia | Caucasian | 82 (schizophrenia) | 50 | WASI† | 86.57 ± 16.16 | 116.44 ± 11.58 | Large, rare deletions related to lower IQ in patients |
| CNV | Lowther et al. (35) (2017) | Cross-sectional | Canada | Caucasian | 546 (SSD) | NA | NA | NA | NA | Pathogenic CNVs related to lower IQ |
| CNV | Hubbard et al. (92) (2021) | Cross-sectional | United Kingdom | Caucasian | 875 (SSD) | NA | WAIS | NA | NA | CNV carriers with schizophrenia had lower IQ |
CNV = copy number variant; NA = not available; SNP = single nucleotide polymorphism; SSD = schizophrenia spectrum disorder; WAIS = Wechsler Adult Intelligence Scale; WASI = Wechsler Abbreviated Scale of Intelligence; WTAR = Wechsler Test of Adult Reading.
↵* Terminology taken from the original articles.
↵† Patients had significantly lower IQs than healthy controls.