Objective Irritability has been proposed to underlie the developmental link between oppositional problems and depression. However, little is known about the genetic and environmental influences on irritability and its overlap with depression. This paper tests the hypothesis that the association between irritability and depression is accounted for by genetic factors. As such, it draws on the notion of “generalist genes” i.e., genes of general effect that underlie phenotypic overlap between disorders. Method The G1219 study, a UK-based twin sample (N=2651), was used in a cross-sectional and longitudinal design. Irritable and headstrong/hurtful dimensions of oppositional behavior were derived using factor analysis. Regression was used to estimate the association between depression and delinquency. Multivariate genetic analyses were used to estimate the genetic overlap between irritability versus headstrong/hurtful behaviors with depression and delinquency respectively. Results Irritability showed a significantly stronger phenotypic relationship with depression than delinquency, whereas headstrong/hurtful behaviors were more strongly related to delinquency than depression. In multivariate genetic analyses, the genetic correlation between irritability and depression (0.70; CI: 0.59-0.82) was significantly higher than that between irritability and delinquency (0.57; CI: 0.45-0.69); conversely, the genetic correlation between headstrong/hurtful behaviors and delinquency (0.80; CI: 0.72-0.86) was significantly higher than that between headstrong/hurtful behaviors and depression (0.46; CI: 0.36-0.57). In longitudinal models, the phenotypic association between irritability at Time 1 and depression at Time 2 was accounted for by the genetic association between irritability and depression at Time1. Conclusions The findings are consistent with the theory that genes with general effects underlie the relationship between irritability and depression.
Context The onset of psychosis is usually preceded by psychotic experiences, but little is known about their causes. The present study investigated the degree of genetic and environmental influences on specific psychotic experiences, assessed dimensionally, in adolescence in the community and in individuals with many, frequent experiences (defined using quantitative cut-offs). The degree of overlap in etiological influences between specific psychotic experiences was also investigated Objective Investigate degree of genetic and environmental influences on specific psychotic experiences, assessed dimensionally, in adolescence in the community and in individuals having many, frequent experiences (defined using quantitative cut-offs). Test degree of overlap in etiological influences between specific psychotic experiences. Design Classic twin design. Structural equation model-fitting. Univariate and bivariate twin models, liability threshold models, DeFries-Fulker extremes analysis and the Cherny Method. Setting Representative community sample of twins from England and Wales. Participants 5059 adolescent twin pairs (Mean age: 16.31 yrs, SD: 0.68 yrs). Main outcome measure Psychotic experiences assessed as quantitative traits (self-rated paranoia, hallucinations, cognitive disorganization, grandiosity, anhedonia; parent-rated negative symptoms). Results Genetic influences were apparent for all psychotic experiences (15-59%) with modest shared environment for hallucinations and negative symptoms (17-24%) and significant nonshared environment (49-64% for the self-rated scales, 17% for Parent-rated Negative Symptoms). Three different empirical approaches converged to suggest that the etiology in extreme groups (most extreme-scoring 5%, 10% and 15%) did not differ significantly from that of the whole distribution. There was no linear change in the heritability across the distribution of psychotic experiences, with the exception of a modest increase in heritability for increasing severity of parent-rated negative symptoms. Of the psychotic experiences that showed covariation, this appeared to be due to shared genetic influences (bivariate heritabilities = .54-.71). Conclusions and Relevance These findings are consistent with the concept of a psychosis continuum, suggesting that the same genetic and environmental factors influence both extreme, frequent psychotic experiences and milder, less frequent manifestations in adolescents. Individual psychotic experiences in adolescence, assessed quantitatively, have lower heritability estimates and higher estimates of nonshared environment than those for the liability to schizophrenia. Heritability varies by type of psychotic experience, being highest for paranoia and parent-rated negative symptoms, and lowest for hallucinations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.