This article profiles the historical twin databases of the secondary education school attached to the Faculty of Education at the University of Tokyo. The school was established in 1948. Every year, about 50 pairs of twins of all sex and zygosity combinations, aged 11–12 years, take an examination, and about 10–20 pairs are admitted based on the results. Three datasets exist: one for applicants (11–12 years old), one for junior and senior high school students (12–18 years old) and one for graduates (18–85 years old). Linking the records from these three databases should facilitate several important research projects, for example, life course genetic epidemiologic studies and the verification of the so-called developmental origins of health and disease hypothesis.

Optimal early cognitive and emotional development are vital to reaching one’s full potential and represent our best chance to improve the mental health of the population. The developmental origins of health and disease (DOHaD) hypothesis posits that adverse perinatal exposures can alter physiology and increase disease risk. As physiological plasticity decreases with age, interventions applied during gestation may hold the most promise for reducing the impact of mental disorders across the lifespan. However, this vast clinical potential remains largely unrealized as the majority of human DOHaD research is observational in nature. The application of more rigorous experimental designs [e.g. Randomized Controlled Trials (RCTs)] not only represents a major step toward unlocking this potential, but are required to fully test the scientific validity of the DOHaD hypothesis as it pertains to mental illness. Here, we argue that the optimization of maternal diet and exercise during pregnancy represents our best chance to improve offspring neurodevelopment and reduce the burden of mental disorders. Follow-up studies of the offspring of pregnant women enrolled in new and existing RCTs of maternal gestational nutrition+exercise interventions are required to determine if acting during pregnancy can prevent and/or meaningfully reduce the prevalence and severity of mental disorders in the population.