Like any other momentous shift in emotion, depression is not an occupation by a foreign army; it is civil insurrection, the subversion of identity's … - Thomas Lewis

While genes are pivotal in establishing some aspects of emotionality, experience plays a central role in turning genes on and off. DNA is not the heart’s destiny; the genetic lottery may determine the cards in your deck, but experience deals the hand you can play. Scientists have proven, for example, that good mothering can override a disadvantageous temperament.

Humanity began in a precarious world where tiny bands foraged and scrimped for food by day, huddled together for warmth by night. With the advent of agriculture came mass aggregation in towns and cities. The industrial revolution took work out of the home, making the populace “a mass of undifferentiated equals, working in a factory or scattered between the factories, the mines, and the offices, bereft forever of the feeling that work was a family affair, done within the household.” Economies prospered as families dissipated. In pursuit of further riches, the information age demands a more thoroughgoing surrender — less time for relationships, less time for children, more time for impersonal everything. Before our lives wither away into dust, we might ponder how much more prosperity human beings can possibly survive.

A number of scientists now believe that somatic concordances like these are not just normal but necessary for mammals. The mammalian nervous system depends for its neurophysiologic stability on a system of interactive coordination, wherein steadiness comes from synchronization with nearby attachment figures.