Aetiological stratification as a conceptual framework for gene-by-environment interaction research in psychiatry

Attachment Style Moderates Polygenic Risk for Posttraumatic Stress in United States Military Veterans: Results From the National Health and Resilience in Veterans Study

BACKGROUND

A polygenic risk score (PRS) derived from genome-wide association studies of posttraumatic stress disorder (PTSD) may inform risk for this disorder. To date, however, no known study has examined whether social environmental factors such as attachment style may moderate the relation between PRS and PTSD.

METHODS

We evaluated main and interactive effects of PRS and attachment style on PTSD symptoms in a nationally representative sample of trauma-exposed European-American U.S. military veterans (N = 2030). PRS was derived from a genome-wide association study of PTSD re-experiencing symptoms (N = 146,660) in the Million Veteran Program cohort. Using one-sample Mendelian randomization with data from the UK Biobank (N = 115,099), we evaluated the effects of re-experiencing PRS and attachment style on PTSD symptoms.

RESULTS

Higher re-experiencing PRS and secure attachment style were independently associated with PTSD symptoms. A significant PRS-by-attachment style interaction was also observed (β = -.11, p = .006), with a positive association between re-experiencing PRS and PTSD symptoms observed only among veterans with an insecure attachment style. One-sample Mendelian randomization analyses suggested that the association between PTSD symptoms and attachment style is bidirectional. PRS enrichment analyses revealed a significant interaction between attachment style and a variant mapping to the IGSF11 gene (rs151177743, p = 2.1 × 10^-7), which is implicated in regulating excitatory synaptic transmission and plasticity.

CONCLUSIONS

Attachment style may moderate polygenic risk for PTSD symptoms, and a novel locus implicated in synaptic transmission and plasticity may serve as a possible biological mediator of this association. These findings may help inform interpersonally oriented treatments for PTSD for individuals with high polygenic risk for this disorder.

Evidence that the association of childhood trauma with psychosis and related psychopathology is not explained by gene-environment correlation: A monozygotic twin differences approach

BACKGROUND

Converging evidence supports childhood trauma as possible causal risk for psychosis and related psychopathology. However, studies have shown that baseline psychotic symptoms may actually increase risk for subsequent victimization, suggesting that exposure to CT is not random but may result from pre-existing vulnerability. Therefore, studies testing whether the association between CT and psychopathology persists when accounting for gene-environment correlation are much needed.

METHODS

A monozygotic (MZ) twin differences approach was used to examine whether differences in CT exposure among MZ twin pairs would be associated with MZ differences in symptoms. As MZ twins are genetically identical, within-pair correlations between CT exposure and psychopathology rule out the possibility that the association is solely attributable to gene-environment correlation. 266 monozygotic twins (133 pairs) from a larger general population study were available for analysis.

RESULTS

CT was associated with symptoms of psychosis (B = 0.62; SE = 0.08, p < .001) and overall psychopathology (B = 43.13; SE = 6.27; p < .001). There were measurable differences within pairs in CT exposure and symptoms, allowing for meaningful within-pair differences. Within-pair differences in CT exposure were associated with within-pair differences in symptoms of psychosis (B = 0.35; SE = 0.16; p = .024), as well as with overall psychopathology (B = 29.22; SE = 12.24; p = .018), anxiety (B = 0.65; SE = 0.21; p = .002) and depression (B = 0.37; SE = 0.18; p = .043).

CONCLUSION

While it is not unlikely that pre-existing vulnerability may increase the risk for traumatic exposures, such gene-environment correlation does not explain away the association between CT and psychopathology. The present findings thus suggest that at least part of the association between CT and psychopathology may be causal.

Stress reactivity links childhood trauma exposure to an admixture of depressive, anxiety, and psychosis symptoms

Childhood trauma exposure has been associated with a clinically relevant mixed phenotype of psychopathology composed of depressive, anxiety, and psychosis symptoms, across healthy and clinical samples. Altered stress-reactivity after exposure to childhood trauma may be a plausible underlying mechanism explaining this association. In a general population sample of female twins (T0 = 564; T1 = 483), associations between childhood trauma exposure and symptom profile (no symptoms, isolated symptoms, or a mixed phenotype) on the one hand, and daily life stress reactivity on the other were investigated. Daily life stress reactivity was measured using the Experience Sampling Method (ESM), and was defined as negative affect reactivity to minor daily life stressors. Individuals exposed to childhood trauma who reported a mixed phenotype of psychopathology showed a significant increase in emotional reactivity to daily life stress (activity and social stress), compared with trauma-exposed individuals without a mixed phenotype. In the trauma-exposed mixed phenotype group, increased emotional reactivity to event-stress predicted more severe symptoms at ± 14 month follow-up. This study found evidence that may link heightened emotional reactivity to stress in individuals with a trauma history to the risk for later comorbid psychopathology.

Review Article: The Role of Molecular Pathological Epidemiology in the Study of Neoplastic and Non-neoplastic Diseases in the Era of Precision Medicine

Molecular pathology diagnostics to subclassify diseases based on pathogenesis are increasingly common in clinical translational medicine. Molecular pathological epidemiology (MPE) is an integrative transdisciplinary science based on the unique disease principle and the disease continuum theory. While it has been most commonly applied to research on breast, lung, and colorectal cancers, MPE can investigate etiologic heterogeneity in non-neoplastic diseases, such as cardiovascular diseases, obesity, diabetes mellitus, drug toxicity, and immunity-related and infectious diseases. This science can enhance causal inference by linking putative etiologic factors to specific molecular biomarkers as outcomes. Technological advances increasingly enable analyses of various -omics, including genomics, epigenomics, transcriptomics, proteomics, metabolomics, metagenomics, microbiome, immunomics, interactomics, etc. Challenges in MPE include sample size limitations (depending on availability of biospecimens or biomedical/radiological imaging), need for rigorous validation of molecular assays and study findings, and paucities of interdisciplinary experts, education programs, international forums, and standardized guidelines. To address these challenges, there are ongoing efforts such as multidisciplinary consortium pooling projects, the International Molecular Pathological Epidemiology Meeting Series, and the Strengthening the Reporting of Observational Studies in Epidemiology-MPE guideline project. Efforts should be made to build biorepository and biobank networks, and worldwide population-based MPE databases. These activities match with the purposes of the Big Data to Knowledge (BD2K), Genetic Associations and Mechanisms in Oncology (GAME-ON), and Precision Medicine Initiatives of the United States National Institute of Health. Given advances in biotechnology, bioinformatics, and computational/systems biology, there are wide open opportunities in MPE to contribute to public health.

Gene-based interaction analysis shows GABAergic genes interacting with parenting in adolescent depressive symptoms

BACKGROUND

Most gene-environment interaction studies (G × E) have focused on single candidate genes. This approach is criticized for its expectations of large effect sizes and occurrence of spurious results. We describe an approach that accounts for the polygenic nature of most psychiatric phenotypes and reduces the risk of false-positive findings. We apply this method focusing on the role of perceived parental support, psychological control, and harsh punishment in depressive symptoms in adolescence.

METHODS

Analyses were conducted on 982 adolescents of Caucasian origin (M_age (SD) = 13.78 (.94) years) genotyped for 4,947 SNPs in 263 genes, selected based on a literature survey. The Leuven Adolescent Perceived Parenting Scale (LAPPS) and the Parental Behavior Scale (PBS) were used to assess perceived parental psychological control, harsh punishment, and support. The Center for Epidemiologic Studies Depression Scale (CES-D) was the outcome. We used gene-based testing taking into account linkage disequilibrium to identify genes containing SNPs exhibiting an interaction with environmental factors yielding a p-value per single gene. Significant results at the corrected p-value of p < 1.90 × 10^-4 were examined in an independent replication sample of Dutch adolescents (N = 1354).

RESULTS

Two genes showed evidence for interaction with perceived support: GABRR1 (p = 4.62 × 10^-5 ) and GABRR2 (p = 9.05 × 10^-6 ). No genes interacted significantly with psychological control or harsh punishment. Gene-based analysis was unable to confirm the interaction of GABRR1 or GABRR2 with support in the replication sample. However, for GABRR2, but not GABRR1, the correlation of the estimates between the two datasets was significant (r (46) = .32; p = .027) and a gene-based analysis of the combined datasets supported GABRR2 × support interaction (p = 1.63 × 10^-4 ).

CONCLUSIONS

We present a gene-based method for gene-environment interactions in a polygenic context and show that genes interact differently with particular aspects of parenting. This accentuates the importance of polygenic approaches and the need to accurately assess environmental exposure in G × E.

The functional and clinical relevance of childhood trauma-related admixture of affective, anxious and psychosis symptoms

OBJECTIVE

Previous work has shown that across different patient samples, patients with childhood trauma are more likely to have co-occurrence of affective, anxious and psychosis symptoms than non-traumatized patients. However, the clinical relevance of trauma-related admixture remains to be established.

METHOD

We examined patients with mood disorder (NEMESIS-2; n = 1260), anxiety disorder (NEMESIS-2; n = 896) or psychotic disorder (GROUP; n = 532) in terms of symptom profiles, quality of life (QOL) and social functioning.

RESULTS

Results showed that mood disorder patients with both trauma and co-occurrence of affective, anxious and psychosis symptoms had a lower QOL (B-12.6, 95% CI -17.7 to -7.5, P < 0.001), more help-seeking behaviour [odds ratio (OR) 2.5, 95% CI 1.1-5.7, P = 0.031] and higher prevalence of substance use disorders (OR 7.8, 95% CI 1.1-58.0, P = 0.044), compared with patients without trauma history and symptom admixture (Trauma-/CL-). Similar results were found in patients with an anxiety disorder. Traumatized patients with a psychotic disorder and admixture showed lower QOL (B-0.6, 95% CI -0.9 to -0.4, P < 0.001), higher prevalence of drug disorders (OR 2.2, 95% CI 1.2-3.9, P = 0.008) and lower global assessment of functioning (B-12.8, 95% CI -17.1 to -8.5, P < 0.001) than Trauma-/CL- patients.

CONCLUSION

Stratification according to childhood trauma exposure thus identifies a phenotype characterized by admixture of affective, anxiety and psychotic symptoms that, when combined, has clinical relevance. Identification of functionally meaningful aetiological subgroups may aid clinical practice.

Integration of molecular pathology, epidemiology and social science for global precision medicine

The precision medicine concept and the unique disease principle imply that each patient has unique pathogenic processes resulting from heterogeneous cellular genetic and epigenetic alterations and interactions between cells (including immune cells) and exposures, including dietary, environmental, microbial and lifestyle factors. As a core method field in population health science and medicine, epidemiology is a growing scientific discipline that can analyze disease risk factors and develop statistical methodologies to maximize utilization of big data on populations and disease pathology. The evolving transdisciplinary field of molecular pathological epidemiology (MPE) can advance biomedical and health research by linking exposures to molecular pathologic signatures, enhancing causal inference and identifying potential biomarkers for clinical impact. The MPE approach can be applied to any diseases, although it has been most commonly used in neoplastic diseases (including breast, lung and colorectal cancers) because of availability of various molecular diagnostic tests. However, use of state-of-the-art genomic, epigenomic and other omic technologies and expensive drugs in modern healthcare systems increases racial, ethnic and socioeconomic disparities. To address this, we propose to integrate molecular pathology, epidemiology and social science. Social epidemiology integrates the latter two fields. The integrative social MPE model can embrace sociology, economics and precision medicine, address global health disparities and inequalities, and elucidate biological effects of social environments, behaviors and networks. We foresee advancements of molecular medicine, including molecular diagnostics, biomedical imaging and targeted therapeutics, which should benefit individuals in a global population, by means of an interdisciplinary approach of integrative MPE and social health science.

Molecular pathological epidemiology gives clues to paradoxical findings

A number of epidemiologic studies have described what appear to be paradoxical associations, where an incongruous relationship is observed between a certain well-established risk factor for disease incidence and favorable clinical outcome among patients with that disease. For example, the "obesity paradox" represents the association between obesity and better survival among patients with a certain disease such as coronary heart disease. Paradoxical observations cause vexing clinical and public health problems as they raise questions on causal relationships and hinder the development of effective interventions. Compelling evidence indicates that pathogenic processes encompass molecular alterations within cells and the microenvironment, influenced by various exogenous and endogenous exposures, and that interpersonal heterogeneity in molecular pathology and pathophysiology exists among patients with any given disease. In this article, we introduce methods of the emerging integrative interdisciplinary field of molecular pathological epidemiology (MPE), which is founded on the unique disease principle and disease continuum theory. We analyze and decipher apparent paradoxical findings, utilizing the MPE approach and available literature data on tumor somatic genetic and epigenetic characteristics. Through our analyses in colorectal cancer, renal cell carcinoma, and glioblastoma (malignant brain tumor), we can readily explain paradoxical associations between disease risk factors and better prognosis among disease patients. The MPE paradigm and approach can be applied to not only neoplasms but also various non-neoplastic diseases where there exists indisputable ubiquitous heterogeneity of pathogenesis and molecular pathology. The MPE paradigm including consideration of disease heterogeneity plays an essential role in advancements of precision medicine and public health.