This chapter lays the foundations for understanding how people, as individuals, can be affected by inequality in ways that lead more unequal societies to have the higher levels of violence and reduced levels of trust and involvement in community life. It looks at each of the three most powerful categories of psychosocial influences on population health: low social status, weak social affiliations, and emotional difficulties early in life. The most important psychosocial risk factors are the most important sources of stress. This means that what the epidemiological research on psychosocial risk factors has achieved is nothing less than the identification of the most powerful sources of chronic stress in modern societies. The personal insecurity that comes from early childhood is connected to the insecurity that can result from low social status. Early stress and the stress of low social status produce many of the same biological, behavioral, and psychological effects.