Objectives: Gene-environment interactions increase the risk of psychosis. The objective of this study was to investigate gene-gene and gene-environment interactions in psychosis, including single nucleotide variants (SNVs) of dopamine-2 receptor (D2R), N-methyl-d-aspartate receptor (NMDAR), and cannabinoid receptor type 1 (CB1R), lifetime cannabis use, and childhood trauma. Methods: Twenty-three SNVs of genes encoding D2R (DRD2: rs1799978, rs7131056, rs6275), NMDAR (GRIN1: rs4880213, rs11146020; GRIN2A: rs1420040, rs11866328; GRIN2B: rs890, rs2098469, rs7298664), and CB1R (CNR1: rs806380, rs806379, rs1049353, rs6454674, rs1535255, rs2023239, rs12720071, rs6928499, rs806374, rs7766029, rs806378, rs10485170, rs9450898) were genotyped in 143 first-episode psychosis patients (FEPp) and 286 community-based controls by Illumina HumanCoreExome-24 BeadChip. Gene-gene and gene-environment associations were assessed using nonparametric Multifactor Dimensionality Reduction software. Results: Single-locus analyses among the 23 SNVs for psychosis and gene-gene interactions were not significant (p > 0.05 for all comparisons); however, both environmental risk factors showed an association with psychosis (p < 0.001). Moreover, gene-environment interactions were significant for an SNV in CNR1 and cannabis use. The best-performing model was the combination of CNR1 rs12720071 and lifetime cannabis use (p < 0.001), suggesting an increased risk of psychosis. Conclusion: Our study supports the hypothesis of gene-environment interactions for psychosis involving T-allele carriers of CNR1 SNVs, childhood trauma, and cannabis use.

Resumo Nós investigamos a viabilidade de incluir a pesquisa de anticorpos anti-NMDAR na avaliação de pacientes em primeiro episódio psicótico em um programa de intervenção precoce no Hemisfério Sul. Anticorpos IgG anti-NMDAR foram avaliados por ELISA em 166 pacientes (64,0% homens), 166 controles de base populacional pareados e 76 irmãos (30,3% homens). Foram realizados teste exato de Fisher e ANOVA. Os anticorpos anti-NMDAR positivos foram mais observados no transtorno afetivo bipolar (10,0%) do que na esquizofrenia (2,4%) ou depressão psicótica (3,1%), embora não tenham sido observadas diferenças significativas. Nossos resultados não são conclusivos quanto à inclusão de anticorpos IgG anti-NMDAR no plasma em protocolos de diagnósticos diferenciais para psicose.

Abstract We investigated the feasibility of including plasma anti-NMDAR antibody screening in the assessment of first-episode psychosis patients in an early intervention programme in the Southern hemisphere. Anti-NMDAR IgG antibodies were assessed by ELISA in 166 patients (64.0% men), 166 matched population-based controls and 76 patients’ siblings (30.3% men). Fisher’s exact test and ANOVA were performed. Positive anti-NMDAR antibody patients were more often observed in bipolar disorder (10.0%) than schizophrenia (2.4%) or psychotic depression (3.1%), although no significant differences were observed. Our results are not conclusive regarding the inclusion of plasma anti-NMDAR IgG antibodies in differential diagnostic protocols for psychosis.

Resumo Nós investigamos a viabilidade de incluir a pesquisa de anticorpos anti-NMDAR na avaliação de pacientes em primeiro episódio psicótico em um programa de intervenção precoce no Hemisfério Sul. Anticorpos IgG anti-NMDAR foram avaliados por ELISA em 166 pacientes (64,0% homens), 166 controles de base populacional pareados e 76 irmãos (30,3% homens). Foram realizados teste exato de Fisher e ANOVA. Os anticorpos anti-NMDAR positivos foram mais observados no transtorno afetivo bipolar (10,0%) do que na esquizofrenia (2,4%) ou depressão psicótica (3,1%), embora não tenham sido observadas diferenças significativas. Nossos resultados não são conclusivos quanto à inclusão de anticorpos IgG anti-NMDAR no plasma em protocolos de diagnósticos diferenciais para psicose.

Abstract We investigated the feasibility of including plasma anti-NMDAR antibody screening in the assessment of first-episode psychosis patients in an early intervention programme in the Southern hemisphere. Anti-NMDAR IgG antibodies were assessed by ELISA in 166 patients (64.0% men), 166 matched population-based controls and 76 patients’ siblings (30.3% men). Fisher’s exact test and ANOVA were performed. Positive anti-NMDAR antibody patients were more often observed in bipolar disorder (10.0%) than schizophrenia (2.4%) or psychotic depression (3.1%), although no significant differences were observed. Our results are not conclusive regarding the inclusion of plasma anti-NMDAR IgG antibodies in differential diagnostic protocols for psychosis.