Studies exploring different candidate genes and IQ in patients with schizophrenia
| Gene | Polymorphism | Study | Design | Country | Ancestry* | Participants, n | IQ measure | Mean IQ ± SD | Association between polymorphism and IQ in patients with SSD | ||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Patients | Healthy controls | Patients | Healthy controls | ||||||||
| 5HT1A-R | −1019 | Bosia et al.59 (2011) | Cross-sectional | Italy | NA | 118 (schizophrenia) | NA | WAIS | 83.46 ± 12.54 | NA | No |
| AKT1 | rs2494732 | Van Winkel et al.60 (2011) | Case–control | Netherlands, Belgium | Caucasian | 611 (NAP) | 590 | WAIS | 94.6 ± 16.5 | NA | No |
| ANK3 | rs1938526 | Cassidy et al.61 (2014) | Cross-sectional | Canada | 102 Caucasian, 71 Other | 173 (FEP) | NA | WAIS | 92.6 ± 15.7 | NA | Yes |
| APOE | rs7412, rs429358 | Vila-Rodriguez et al.62 (2017) | Case–control | Canada | 60 Caucasian, 13 Asian, 13 Other 60:13:13 (69.8 % Caucasian) | 86 (FEP) | 39 | NAART† | 100.45 ± 8.01 | 107.54 ± 6.75 | No |
| CNNM2 | rs7914558 | Rose et al.63 (2014) | Case–control | Ireland | NA | 400 (SSD) | 160 | WAIS† | 91.23 ± 18.39 | 121.4 ± 14.6 | No |
| CPLX2 | rs6868608, rs2443541, rs2243404, rs4242187, rs10072860, rs4868539, rs1366116, rs3892909, rs3822674, rs56934064 | Begemann et al.64 (2010) | Case–control | Germany | Caucasian | 1071 (SSD) | 1079 | MWT-B | NA | NA | No |
| CSMD1 | rs10503253 | Donohoe et al.65 (2013) | Case–control | Ireland | Caucasian | 387 (SSD) | 205 | WAIS† | 89.74 ± 17.46 | 118.3 ± 13.89 | Yes |
| FKBP5 | rs1360780, rs9470080, rs4713902, rs9394309 | Green et al.66 (2015) | Case–control | Australia | 98% Caucasian | 617 (SSD) | 659 | WTAR† | 97.49 ± 15.04 | 105.47 ± 10.67 | No |
| FOLH1 | rs202676 | Zink et al.67 (2020) | Case–control | United States | Caucasian and African American | 57 (FEP) | 65 | HART | 100.7 ± 10.6 | 104.3 ± 10.6 | Yes |
| GRIN2A, GRIN2B, GRIN3A, GRM1, GRM3, GRM4, GRM5, GRM7, GRM8 | 43 SNPs | Chaumette et al.68 (2020) | Cohort | Canada | Caucasian | 148 (FEP) | NA | WAIS | 92.8 ± 15.4 | NA | Yes (only rs1396409 in GRM7) |
| GRM5 | rs60954128, rs3824927 | Matosin et al.69 (2018) | Case–control | Australia | Caucasian | 249 (schizophrenia) | 261 | WASI† | 102.69 ± 13.94 | 118.01 ± 10.26 | Yes (only rs3824927) |
| HPS4 | rs4822724, rs61276843, rs9608491, rs713998, rs2014410 | Kuratomi et al.70 (2013) | Case–control | Japan | East Asian | 240 (schizophrenia) | 240 | JART† | 92.4 ± 10.4 | 103.4 ± 10.7 | No |
| IL1B | rs16944 | Fatjó-Vilas et al.71 (2012) | Case–control | Spain | European | 48 (schizophrenia) | 46 | WAIS† | 89.04 ± 15.27 | 107.81 ± 12.81 | No |
| LOC100128714 | rs4906844 | Bakken et al.72 (2011) | Case–control | Norway | Caucasian | 208 (SSD) | 368 | WASI† | 103.4 ± 14.0 | 113.5 ± 9.7 | No |
| MHC, TCF4, NRGN | rs6904071, rs13219354, rs3131296, rs6932590, rs9960767, rs12807809 | Walters et al.73 (2013) | Case–control | Germany | Caucasian | 342 (schizophrenia) | 2244 | WAIS† | 102.2 ± 18.0 | 113.76 ± 14.3 | Yes (only rs6904071 in MHC) |
| MIR137 | rs1625579 | Green et al.74 (2013) | Case–control | Australia | Australian | 617 (SSD) | 764 | WTAR† | 97.49 ± 15.04 | 105.47 ± 10.67 | Yes (only together with negative symptoms) |
| NOS1 | rs6490121 | Donohoe et al.75 (2009) | Case–control | Ireland | Caucasian | 349 (SSD) | 230 | WAIS† | 91.53 ± 18.2 | 122.93 ± 15.13 | Yes (only for verbal IQ) |
| NOSI | rs6490121, rs3782206 | Zhang et al.76 (2015) | Case–control | China | East Asian | 580 (schizophrenia) | 720 | WAIS† | 95.99 ± 14.67 | 106.49 ± 13.99 | No |
| NRG1 | rs2439272, rs6988339 | Ananloo et al.77 (2020) | Case–control | Iran | Asian | 276 (schizophrenia) | 193 | WAIS† | 74.35 ± 11.07 | 105.19 ± 7.25 | Yes |
| NRGN | rs12807809, rs12278912 | Ohi et al.78 (2013) | Case–control | Japan | East Asian | 157 (schizophrenia) | 257 | WAIS† | NA | NA | Yes (only for the diplotype) |
| NRN1 | 19 SNPs | Chandler et al.79 (2010) | Case–control | Australia | Caucasian | 336 (schizophrenia) | 172 | SILS† | 89.9 ± 14.2 | 108.2 ± 8.4 | Yes (for rs1475157, rs9405890) |
| NRN1 | 11 SNPs | Fatjo-Vilas et al.80 (2016) | Case–control | Spain | Caucasian | 697 (SSD) | 668 | WAIS† | 89.02 ± 15.37 | 99.48 ± 13.64 | Yes (for the haplotype rs9763180, rs1048432, rs4960155, rs9379002, rs9405890, rs1475157, before statistical correction) |
| OXTR | rs2254298, rs53576, rs115324487 | Montag et al.81 (2012) | Case–control | Germany | Caucasian | 145 (schizophrenia) | 145 | MWT-B† | 103.96 ± 13.5 | 108.96 ± 13.4 | No |
| OXTR | rs143908202, rs150746704, rs115324487, rs61740241 | Veras et al.82 (2018) | Case–control | United States | Caucasian, Hispanic, African American and Other | 48 (SSD) | 25 | WAIS† | 84.05 ± 11.75 | 102.9 ± 15.3 | Yes (only for nonverbal IQ) |
| S100B | rs2839357, rs1051169, rs9722 | Zhai et al.83 (2012) | Case–control | China | East Asian | 434 (schizophrenia) | 412 | WAIS† | 97.13 ± 14.87 | 108.52 ± 13.89 | No |
| ST8SIA2 | rs4586379, rs2035645, rs4777974, rs3784735 | Fullerton et al.84 (2018) | Case–control | Australia | 88.1% European, 3.5% Asian, 8.4% Unknown | 281 (SSD) | 172 | WASI† | 104 | 119 | No |
| TH | rs10770141 | Horiguchi et al.85 (2014) | Case–control | Japan | East Asian | 132 (schizophrenia) | 282 | WAIS† | 103.75 ± 11.15 | 106.9 ± 8.7 | Yes |
| ZNF804A | rs1344706 | Walters et al.86 (2010) | Case–control | Ireland | Caucasian | 297 (schizophrenia) | 165 | WAIS† | 88.0 ± 16.26 | 122.26 ± 13.83 | Yes (only for high IQ) |
| ZNF804A | rs1344706 | Chen et al.87 (2012) | Case–control | China | East Asian | 531 (schizophrenia) | 442 | WAIS† | 97.09 ± 14.72 | 109.50 ± 11.88 | Yes (only for high IQ) |
FEP = first episode of psychosis; HART = Hopkins Adult Reading Test; JART = Japanese version of the National Adult Reading Test; MWT-B = Mehrfachwahl-Wortschatz Test B; NA = not available; NAART = North American Adult Reading Test; NAP = non-affective psychosis; SD = standard deviation; SILS = Shipley Institute of Living Scale test; 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.