Schizophrenia polygenic risk score and 20-year course of illness in psychotic disorders

Special Article: Translational Science Update. Pharmacological Implications of Emerging Schizophrenia Genetics: Can the Bridge From 'Genomics' to 'Therapeutics' be Defined and Traversed?

Recent schizophrenia genome-wide association studies (GWAS) have identified genomic variants of common and rare frequency, significantly associated with schizophrenia. While numerous functional genomics efforts are ongoing to elucidate the biological effects of schizophrenia risk variants, a consideration of their therapeutic implications is timely and imperative, for patients as well as for an iterative effect on elucidating the underlying biology and pathophysiology of illness. The current article reviews efforts to translate emerging schizophrenia genomics into novel approaches to target discovery and therapeutic intervention. Though the path from 'genetic risk to therapy' is far from straightforward, there are provocative early possibilities that harbor the promise of treatment based on causation rather than phenomenology, as well as 'precision psychiatry,' a basis for stratifying patients to enable more precise and effective, personalized therapy.

Prospective Long-Term Cohort Study of Subjects With First-Episode Psychosis Examining Eight Major Outcome Domains and Their Predictors: Study Protocol

Background: Our current ability to predict the long-term course and outcome of subjects with a first-episode of psychosis (FEP) is limited. To improve our understanding of the long-term outcomes of psychotic disorders and their determinants, we designed a follow-up study using a well-characterized sample of FEP and a multidimensional approach to the outcomes. The main goals were to characterize the long-term outcomes of psychotic disorders from a multidimensional perspective, to address the commonalities and differential characteristics of the outcomes, and to examine the common and specific predictors of each outcome domain. This article describes the rationale, methods, and design of a longitudinal and naturalistic study of subjects with epidemiologically defined first-admission psychosis. Methods: Eligible subjects were recruited from consecutive admissions between January 1990 and December 2009. Between January 2018 and June 2021, we sought to trace, re-contact, and re-interview the subjects to assess the clinical course, trajectories of symptoms and functioning, and the different outcomes of psychotic disorders. Since this is a naturalistic study, the research team will not interfere with the subjects' care and treatment. Predictors include antecedent variables, first-episode characteristics, and illness-related variables over the illness course. We assess eight outcome domains at follow-up: psychopathology, psychosocial functioning, self-rated personal recovery, self-rated quality of life, cognitive performance, neuromotor dysfunction, medical and psychiatric comorbidities, and mortality rate. The range of the follow-up period will be 10-31 years with an estimated mean of 20 years. We estimate that more than 50% of the baseline sample will be assessed at follow-up. Discussion: The study design was driven by the increasing need to refine the ability to predict the different clinical outcomes in FEP, and it aims to close current gaps in knowledge, with a broad approach to both the definition of outcomes and their determinants. To the best of our knowledge, this study is one of the few attempting to characterize the very long-term outcome of FEP and the only study addressing eight major outcome domains. We hope that this study helps to better characterize the long-term outcomes and their determinants, enabling better risk stratification and individually tailored, person-based interventions.

Genetic liability in individuals at ultra-high risk of psychosis: A comparison study of 9 psychiatric traits

Individuals at ultra-high risk (UHR) of psychosis are characterised by the emergence of attenuated psychotic symptoms and deterioration in functioning. In view of the high non-psychotic comorbidity and low rates of transition to psychosis, the specificity of the UHR status has been called into question. This study aims to (i) investigate if the UHR construct is associated with the genetic liability of schizophrenia or other psychiatric conditions; (ii) examine the ability of polygenic risk scores (PRS) to discriminate healthy controls from UHR, remission and conversion status. PRS was calculated for 210 youths (nUHR = 102, nControl = 108) recruited as part of the Longitudinal Youth at Risk Study (LYRIKS) using nine psychiatric traits derived from twelve large-scale psychiatric genome-wide association studies as discovery datasets. PRS was also examined to discriminate UHR-Healthy control status, and healthy controls from UHR remission and conversion status. Result indicated that schizophrenia PRS appears to best index the genetic liability of UHR, while trend level associations were observed for depression and cross-disorder PRS. Schizophrenia PRS discriminated healthy controls from UHR (R2 = 7.9%, p = 2.59 x 10-3, OR = 1.82), healthy controls from non-remitters (R2 = 8.1%, p = 4.90 x 10-4, OR = 1.90), and converters (R2 = 7.6%, p = 1.61 x 10-3, OR = 1.82), with modest predictive ability. A trend gradient increase in schizophrenia PRS was observed across categories. The association between schizophrenia PRS and UHR status supports the hypothesis that the schizophrenia polygenic liability indexes the risk for developing psychosis.

Schizophrenia Polygenic Risk and Brain Structural Changes in Methamphetamine-Associated Psychosis in a South African Population

Background

The genetic architecture of psychotic disorders is complex, with hundreds of genetic risk loci contributing to a polygenic model of disease. Overlap in the genetics of psychotic disorders and brain measures has been found in European populations, but has not been explored in populations of African ancestry. The aim of this study was to determine whether a relationship exists between a schizophrenia-derived PRS and (i) methamphetamine associated psychosis (MAP), and (ii) brain structural measures, in a South African population.

Methods

The study sample consisted of three participant groups: 31 individuals with MAP, 48 with apsychotic methamphetamine dependence, and 49 healthy controls. Using PRSice, PRS was generated for each of the participants with GWAS summary statistics from the Psychiatric Genomics Consortium Schizophrenia working group (PGC-SCZ2) as the discovery dataset. Regression analyses were performed to determine associations of PRS, with diagnosis, whole brain, and regional gray and white matter measures.

Results

Schizophrenia-derived PRS did not significantly predict MAP diagnosis. After correction for multiple testing, no significant associations were found between PRS and brain measures across all groups.

Discussion

The lack of significant associations here may indicate that the study is underpowered, that brain volumes in MAP are due to factors other than polygenic risk for schizophrenia, or that PRS derived from a largely European discovery set has limited utility in individuals of African ancestry. Larger studies, that include diverse populations, and more nuanced brain measures, may help elucidate the relationship between schizophrenia-PRS, brain structural changes, and psychosis.

Conclusion

This research presents the first PRS study to investigate shared genetic effects across psychotic disorders and brain structural measures in an African population. Ancestrally comparable discovery datasets may be useful for future African genetic research.

Evaluating the effect of birth weight on brain volumes and depression: An observational and genetic study using UK Biobank cohort

Background.

Birth weight influences not only brain development, but also mental health outcomes, including depression, but the underlying mechanism is unclear.

Methods.

The phenotypic data of 12,872–91,009 participants (59.18–63.38% women) from UK Biobank were included to test the associations between the birth weight, depression, and brain volumes through the linear and logistic regression models. As birth weight is highly heritable, the polygenic risk scores (PRSs) of birth weight were calculated from the UK Biobank cohort (154,539 participants, 56.90% women) to estimate the effect of birth weight-related genetic variation on the development of depression and brain volumes. Finally, the mediation analyses of step approach and mediation analysis were used to estimate the role of brain volumes in the association between birth weight and depression. All analyses were conducted sex stratified to assess sex-specific role in the associations.

Result.

We observed associations between birth weight and depression (odds ratio [OR] = 0.968, 95% confidence interval [CI] = 0.957–0.979, p = 2.29 × 10⁻⁶). Positive associations were observed between birth weight and brain volumes, such as gray matter (B = 0.131, p = 3.51 × 10⁻⁷⁴) and white matter (B = 0.129, p = 1.67 × 10⁻⁷⁴). Depression was also associated with brain volume, such as left thalamus (OR = 0.891, 95% CI = 0.850–0.933, p = 4.46 × 10⁻⁵) and right thalamus (OR = 0.884, 95% CI = 0.841–0.928, p = 2.67 × 10⁻⁵). Additionally, significant mediation effects of brain volume were found for the associations between birth weight and depression through steps approach and mediation analysis, such as gray matter (B = –0.220, p = 0.020) and right thalamus (B = –0.207, p = 0.014).

Conclusions.

Our results showed the associations among birth weight, depression, and brain volumes, and the mediation effect of brain volumes also provide evidence for the sex-specific of associations.

Pleiotropy of polygenic factors associated with focal and generalized epilepsy in the general population

Epilepsy is clinically heterogeneous, and neurological or psychiatric comorbidities are frequently observed in patients. It has not been tested whether common risk variants for generalized or focal epilepsy are enriched in people with other disorders or traits related to brain or cognitive function. Here, we perform two brain-focused phenome association studies of polygenic risk scores (PRS) for generalized epilepsy (GE-PRS) or focal epilepsy (FE-PRS) with all binary brain or cognitive function-related traits available for 334,310 European-ancestry individuals of the UK Biobank. Higher GE-PRS were associated with not having a college or university degree (P = 3.00x10-4), five neuroticism-related personality traits (P<2.51x10-4), and having ever smoked (P = 1.27x10-6). Higher FE-PRS were associated with several measures of low educational attainment (P<4.87x10-5), one neuroticism-related personality trait (P = 2.33x10-4), having ever smoked (P = 1.71x10-4), and having experienced events of anxiety or depression (P = 2.83x10-4). GE- and FE-PRS had the same direction of effect for each of the associated traits. Genetic factors associated with GE or FE showed similar patterns of correlation with genetic factors associated with cortical morphology in a subset of the UKB with 16,612 individuals and T1 magnetic resonance imaging data. In summary, our results suggest that genetic factors associated with epilepsies may confer risk for other neurological and psychiatric disorders in a population sample not enriched for epilepsy.

Genetics of Treatment Outcomes in Major Depressive Disorder: Present and Future

Pharmacogenetic testing is a useful and increasingly widespread tool to assist in antidepressant prescription. More than ten antidepressants (including tricyclics, selective serotonin reuptake inhibitors and venlafaxine) have already genetic biomarkers of response/side effects in clinical guidelines and drug labels. These are represented by functional genetic variants in genes coding for cytochrome enzymes (CYP2D6 and CYP2C19). Depending on the predicted metabolic activity, guidelines provide recommendations on drug choice and dosing. Despite not conclusive, the current evidence suggests that testing can be useful in patients who did not respond or tolerate at least one previous pharmacotherapy. However, the current recommendations are based on pharmacokinetic genes only (CYP450 enzymes), while pharmacodynamic genes (modulating antidepressant mechanisms of action in the brain) are still being studied because of their greater complexity. This may be captured by polygenic risk scores, which reflect the cumulative contribution of many genetic variants to a trait, and they may provide future clinical applications of pharmacogenetics. A more extensive use of genotyping in clinical practice may lead to improvement in treatment outcomes thanks to personalized treatments, but possible ethical issues and disparities should be taken into account and prevented.