Prenatal programming of behavior: a twin-study perspective

Developmental Instability and Individual Variation in Brain Development

Research on the origin of neurodevelopmental disorders has traditionally been pursued within a constrained, disorder-specific perspective. The developmental instability (DI) model described here offers a broader approach based on the evolutionary genetics of normal variation, reflecting our understanding that the processes generating genetic diversity are not unique to any specific disorder. The DI model helps account for shared features, including atypical functional and anatomic asymmetries, reduced general intellectual functioning, and complex patterns of heritability, across different types of neural variation. The model suggests research strategies that may help illuminate the specific and unique causal factors characterizing different types of neural variation.

[Life course genetic epidemiologic study based on longitudinal twin-family data: a new perspective]

Family-based life course epidemiology is the approach to clarify long-term effects of accumulations and chains of biological and social risk exposures in one's life trajectory, namely, before and during conception, infancy, childhood, young adulthood and later adult life. Both genetic and environmental factors are considered. One of the theoretical rationales is the 'developmental origin of health and disease (DOHaD)' hypothesis. According to this theory, the causes of adult diseases are attributed to predictive adaptive responses and biological programming or epigenetic changes during a critical period of early life. If the environment later in life after birth is different from what is predicted, a mismatch has happened, leading to the development of a disease. This theory is supported by many epidemiologic studies, animal experiments, and evolution theory of biology. Longitudinal twin-family data are very powerful and useful information in the family-based life course genetic epidemiologic study.

Fetal origins of mental health: evidence and mechanisms

The concept of fetal programming states that changes in the fetal environment during sensitive periods of organ development may cause long-lasting changes in the structure and functioning of these organs later in life and influence the risk for chronic diseases such as coronary heart disease and type 2 diabetes. Fetal growth is a summary marker of the fetal environment and is reflected by relatively easy-to-obtain measures of size at birth such as birth weight. In the last two decades, a body of evidence emerged linking fetal growth with behavioural and mental health outcomes later in life. Cognitive functioning and behavioural problems in childhood, in particular inattention/hyperactivity, have been shown to be inversely related to fetal growth. Although results are mixed, risk for personality disorders and schizophrenia seems to be linked with fetal growth and adversity, while the evidence for mood disorders is weak. Vulnerability for psychopathology may also be influenced by prenatal adversity. There is evidence for associations of fetal growth with temperament in childhood as well as stress reactivity and distress. The associations of fetal growth with mental health later in life are potentially caused by specific prenatal factors such as maternal smoking, alcohol, toxins/drugs, nutrition, psychosocial stress and infection during pregnancy. The mechanisms likely involve changes in neurodevelopment and in the set point of neuroendocrine systems, and there is evidence that prenatal adversity interacts with genetic and postnatal environmental factors. Future studies should examine the effects of specific prenatal factors and attempt to disentangle genetic and prenatal environmental effects.