Part One provided an introduction to individual development, focusing on neuropsychological and behavioural changes that are mediated by early environments within the family and the education system. Good psychosocial and nutritional support and exercise are important for a person to experience good health and a sense of well-being. This part reviews the need to understand the impact of legal and illegal drug use and the increasing use of the internet on various social groups. Although risks of alcohol and other drug use are widespread across society, the impacts on health and increased vulnerability to addictive behaviours are greater in disadvantaged groups. The underlying psychological factors of stigma and exclusion from society, combined with a more sedentary lifestyle related to increasing use of computers, are resulting in modern epidemics such as obesity. Although a wide range of interventions are being developed to support individuals, upstream policies relating to welfare and community infrastructure are needed.