The next 10 years of behavioural genomic research

Nonshared environment: Real but random

Background

In the excitement about genomics, it is easy to lose sight of one of the most important findings from behavioural genetics: At least half of the variance of psychopathology is caused by environmental effects that are not shared by children growing up in the same family, which includes error of measurement. However, a 30-year search for the systematic causes of nonshared environment in a line-up of the usual suspects, especially parenting, has not identified the culprits.

Method

I briefly review this research, but primarily consider the conceptual framework of the search for 'missing' nonshared environmental effects.

Results

The search has focused on exogenous events like parenting, but nonshared environment might not be caused by anything we would call an event. Instead, it might reflect endogenous processes such as noisy biological systems (such as somatic mutations and epigenetics) or, at a psychological level, idiosyncratic subjective perceptions of past and present experiences, which could be called nonshared environmental experience to distinguish it from exogenous events. Although real, nonshared environment might be random in the philosophy of science sense of being unpredictable, even though it can have stable effects that predict subsequent behaviour.

Conclusion

I wade into the weeds of randomness and suggest that this so-called 'gloomy prospect' might not be so gloomy.

How early environment influences the developing brain and long-term mental health

The March 2024 issue of JCPP Advances features two neuroimaging studies that investigate links between early environmental risk factors for mental health problems, brain development and psychopathology in children and young adults. The papers provide new insights into how adverse environments and negative experiences in childhood increase risk for depression and mental health problems, and how this may or may not be mediated, or moderated, by individual differences in the brain.

Children of parents with depression or anxiety: Long-term follow-up, causality and resilience

Three papers in the December issue (2023) of JCPP Advances focus on children of parents with depression or anxiety. They highlight the value of using prospective longitudinal data to improve the understanding about the development of children of parents with depression or anxiety from early childhood to young adulthood. They contribute to an advanced understanding of long-term outcomes, causality and resilience for children of parents with depression or anxiety.

Maximizing the value of twin studies in health and behaviour

In the classical twin design, researchers compare trait resemblance in cohorts of identical and non-identical twins to understand how genetic and environmental factors correlate with resemblance in behaviour and other phenotypes. The twin design is also a valuable tool for studying causality, intergenerational transmission, and gene-environment correlation and interaction. Here we review recent developments in twin studies, recent results from twin studies of new phenotypes and recent insights into twinning. We ask whether the results of existing twin studies are representative of the general population and of global diversity, and we conclude that stronger efforts to increase representativeness are needed. We provide an updated overview of twin concordance and discordance for major diseases and mental disorders, which conveys a crucial message: genetic influences are not as deterministic as many believe. This has important implications for public understanding of genetic risk prediction tools, as the accuracy of genetic predictions can never exceed identical twin concordance rates.

Why we need families in genomic research on developmental psychopathology

Background

Fundamental questions about the roles of genes, environments, and their interplay in developmental psychopathology have traditionally been the domain of twin and family studies. More recently, the rapidly growing availability of large genomic datasets, composed of unrelated individuals, has generated novel insights. However, there are major stumbling blocks. Only a small fraction of the total genetic influence on childhood psychopathology estimated from family data is captured with measured DNA. Moreover, genetic influence identified using DNA is often confounded with indirect genetic effects of relatives, population stratification and assortative mating.

Methods

The goal of this paper is to review how combining DNA-based genomic research with family-based quantitative genetics helps to address key issues in genomics and push knowledge further.

Results

We focus on three approaches to obtaining more accurate and novel genomic findings on the developmental aetiology of psychopathology: (a) using knowledge from twin and family studies, (b) triangulating with twin and family studies, and (c) integrating data and methods with twin and family studies.

Conclusion

We support the movement towards family-based genomic research, and show that developmental psychologists are particularly well-placed to contribute hypotheses, analysis tools, and data.

The nature of psychopathology

Readers of JCPP Advances known that the dominant classification system (Diagnostic and Statistical Manual of Mental Disorders) in psychiatry and psychology conceptualizes psychopathology as discrete diagnostic categories. This measurement model builds on a strong assumption of a clear discontinuity between individuals who meet criteria for a diagnosis and those who don't fulfill diagnostic criteria. During the past decades we have seen huge efforts to test this assumption and explore alternative models, such as research from the hierarchical taxonomy of psychopathology consortia. Key findings of these efforts are reviewed and discussed in the December issue of JCPP Advances.