Table 5

Studies exploring different candidate genes and IQ in patients with schizophrenia

GenePolymorphismStudyDesignCountryAncestry*Participants, nIQ measureMean IQ ± SDAssociation between polymorphism and IQ in patients with SSD
PatientsHealthy controlsPatientsHealthy controls
5HT1A-R−1019Bosia et al.59 (2011)Cross-sectionalItalyNA118 (schizophrenia)NAWAIS83.46 ± 12.54NANo
AKT1rs2494732Van Winkel et al.60 (2011)Case–controlNetherlands, BelgiumCaucasian611 (NAP)590WAIS94.6 ± 16.5NANo
ANK3rs1938526Cassidy et al.61 (2014)Cross-sectionalCanada102 Caucasian, 71 Other173 (FEP)NAWAIS92.6 ± 15.7NAYes
APOErs7412, rs429358Vila-Rodriguez et al.62 (2017)Case–controlCanada60 Caucasian, 13 Asian, 13 Other
60:13:13 (69.8 % Caucasian)
86 (FEP)39NAART100.45 ± 8.01107.54 ± 6.75No
CNNM2rs7914558Rose et al.63 (2014)Case–controlIrelandNA400 (SSD)160WAIS91.23 ± 18.39121.4 ± 14.6No
CPLX2rs6868608, rs2443541, rs2243404, rs4242187, rs10072860, rs4868539, rs1366116, rs3892909, rs3822674, rs56934064Begemann et al.64 (2010)Case–controlGermanyCaucasian1071 (SSD)1079MWT-BNANANo
CSMD1rs10503253Donohoe et al.65 (2013)Case–controlIrelandCaucasian387 (SSD)205WAIS89.74 ± 17.46118.3 ± 13.89Yes
FKBP5rs1360780, rs9470080, rs4713902, rs9394309Green et al.66 (2015)Case–controlAustralia98% Caucasian617 (SSD)659WTAR97.49 ± 15.04105.47 ± 10.67No
FOLH1rs202676Zink et al.67 (2020)Case–controlUnited StatesCaucasian and African American57 (FEP)65HART100.7 ± 10.6104.3 ± 10.6Yes
GRIN2A, GRIN2B, GRIN3A, GRM1, GRM3, GRM4, GRM5, GRM7, GRM843 SNPsChaumette et al.68 (2020)CohortCanadaCaucasian148 (FEP)NAWAIS92.8 ± 15.4NAYes (only rs1396409 in GRM7)
GRM5rs60954128, rs3824927Matosin et al.69 (2018)Case–controlAustraliaCaucasian249 (schizophrenia)261WASI102.69 ± 13.94118.01 ± 10.26Yes (only rs3824927)
HPS4rs4822724, rs61276843, rs9608491, rs713998, rs2014410Kuratomi et al.70 (2013)Case–controlJapanEast Asian240 (schizophrenia)240JART92.4 ± 10.4103.4 ± 10.7No
IL1Brs16944Fatjó-Vilas et al.71 (2012)Case–controlSpainEuropean48 (schizophrenia)46WAIS89.04 ± 15.27107.81 ± 12.81No
LOC100128714rs4906844Bakken et al.72 (2011)Case–controlNorwayCaucasian208 (SSD)368WASI103.4 ± 14.0113.5 ± 9.7No
MHC, TCF4, NRGNrs6904071, rs13219354, rs3131296, rs6932590, rs9960767, rs12807809Walters et al.73 (2013)Case–controlGermanyCaucasian342 (schizophrenia)2244WAIS102.2 ± 18.0113.76 ± 14.3Yes (only rs6904071 in MHC)
MIR137rs1625579Green et al.74 (2013)Case–controlAustraliaAustralian617 (SSD)764WTAR97.49 ± 15.04105.47 ± 10.67Yes (only together with negative symptoms)
NOS1rs6490121Donohoe et al.75 (2009)Case–controlIrelandCaucasian349 (SSD)230WAIS91.53 ± 18.2122.93 ± 15.13Yes (only for verbal IQ)
NOSIrs6490121, rs3782206Zhang et al.76 (2015)Case–controlChinaEast Asian580 (schizophrenia)720WAIS95.99 ± 14.67106.49 ± 13.99No
NRG1rs2439272, rs6988339Ananloo et al.77 (2020)Case–controlIranAsian276 (schizophrenia)193WAIS74.35 ± 11.07105.19 ± 7.25Yes
NRGNrs12807809, rs12278912Ohi et al.78 (2013)Case–controlJapanEast Asian157 (schizophrenia)257WAISNANAYes (only for the diplotype)
NRN119 SNPsChandler et al.79 (2010)Case–controlAustraliaCaucasian336 (schizophrenia)172SILS89.9 ± 14.2108.2 ± 8.4Yes (for rs1475157, rs9405890)
NRN111 SNPsFatjo-Vilas et al.80 (2016)Case–controlSpainCaucasian697 (SSD)668WAIS89.02 ± 15.3799.48 ± 13.64Yes (for the haplotype rs9763180, rs1048432, rs4960155, rs9379002, rs9405890, rs1475157, before statistical correction)
OXTRrs2254298, rs53576, rs115324487Montag et al.81 (2012)Case–controlGermanyCaucasian145 (schizophrenia)145MWT-B103.96 ± 13.5108.96 ± 13.4No
OXTRrs143908202, rs150746704, rs115324487, rs61740241Veras et al.82 (2018)Case–controlUnited StatesCaucasian, Hispanic, African American and Other48 (SSD)25WAIS84.05 ± 11.75102.9 ± 15.3Yes (only for nonverbal IQ)
S100Brs2839357, rs1051169, rs9722Zhai et al.83 (2012)Case–controlChinaEast Asian434 (schizophrenia)412WAIS97.13 ± 14.87108.52 ± 13.89No
ST8SIA2rs4586379, rs2035645, rs4777974, rs3784735Fullerton et al.84 (2018)Case–controlAustralia88.1% European, 3.5% Asian, 8.4% Unknown281 (SSD)172WASI104119No
THrs10770141Horiguchi et al.85 (2014)Case–controlJapanEast Asian132 (schizophrenia)282WAIS103.75 ± 11.15106.9 ± 8.7Yes
ZNF804Ars1344706Walters et al.86 (2010)Case–controlIrelandCaucasian297 (schizophrenia)165WAIS88.0 ± 16.26122.26 ± 13.83Yes (only for high IQ)
ZNF804Ars1344706Chen et al.87 (2012)Case–controlChinaEast Asian531 (schizophrenia)442WAIS97.09 ± 14.72109.50 ± 11.88Yes (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.