Insights into neuroscience from the representative birth cohort samples of a multidisciplinary longitudinal study

Longitudinal studies on population representative samples offer unique insights. The Estonian Children Personality Behaviour and Health Study (ECPBHS; EstChild) was launched in 1998 on two birth cohort samples at age 9 or 15 with an exceptional participation rate, has been monitored at ages 15, 18, 25 and 33, and also recruited parents of the target subjects. This multidisciplinary investigation has been focused on behavioural neuroscience, illuminating findings on what could be discerned from biomarkers, candidate genes, gene × environment interactions, and epigenetic markers in representative samples, and in birth cohorts living through societal transformation. ECPBHS analysed how biomarkers and lifestyle are associated with real-life behaviours and developmental trajectories, phenotypes such as neuroticism, bulimia, aggressiveness or attention deficit, and outcomes from incidence of psychiatric disorders to the obtaining of university education. Novel evidence has been observed on clustering of fears and the inner structure of impulsivity and reward sensitivity, together with clues how these may have co-emerged with metabolic types. New insights have been provided to understand the classic biomarkers, cholesterol and platelet monoamine oxidase activity, as well as several functional gene variants. Hypotheses how to synthetise molecular genetics and sociology, how sex or gender matters in the light of gene × environment interactions and how family and parental roles shape the behaviour of offspring have been put forward. The ECPBHS has offered clues on why in biological psychiatry many replication attempts are predestined to fail, and how to learn from such failures.