The Early Life Environment and Adult Cognitive and Mental Health

Abstract

Many diverse adult diseases, from diabetes to dementia, are increasingly viewed as arising, in part, from early life environmental influences. The so-called Developmental Origins of Health and Disease (DOHaD) research paradigm offers the potential to improve our understanding of the etiology of many hard-to-treat adult diseases by focusing researcher’s attention on the pre and post-natal and early childhood years, where small interventions could pay large dividends later on. Along with great potential, the DOHaD framework offers great challenges, as it is logistically and conceptually difficult to investigate the environmental origins of chronic diseases that may manifest only decades after harmful exposures. This dissertation presents a series of five original studies that sought to answer open empirical questions about the developmental origins of health and disease focusing on early-life factors that influence the health and aging of the brain. Three increasingly broad "levels" of the early life environment are considered across three sequential dissertation chapters: (1) the individual micro-physical level, (2) the family level, and (3) the neighborhood level. At each level this dissertation considers at least one exposure that has relevance to researchers and policy makers, either because, like exposure to neighborhood vegetation / greenery, it may offer a good route for intervention (e.g., the exposure is potentially modifiable) or because, like exposure to the heavy metal lead, it is understood to be more widespread than previously assumed. Studies were conducted using data from two population-representative longitudinal birth cohorts, the New Zealand-based Dunedin Multidisciplinary Health and Development Study (born in 1972-1973) and the United Kingdom-based Environmental Risk Longitudinal Twin Study (born in 1994-1995). Across the five studies, results supported the DOHaD framework and provided new evidence about the long-term consequences of childhood exposure to lead, adversity (e.g., physical and emotional abuse, household dysfunction, etc.), and neighborhood disadvantage. These negative early life events / exposures at the micro-physical, family, and neighborhood-levels associated, across multiple decades, with subtle and diverse poor brain-related outcomes later in life, including diminished cognitive capacity, increased symptoms of psychopathology, altered epigenetic controls, disadvantageous personality styles, and worse physical health. Results collectively reinforce the view that the early life represents a profound window of vulnerability and opportunity, with a lifespan perspective offering great potential for more efficacious public health research, clinical practice, and policy, as the diseases of the adult likely have roots in the life of the child.