A HOLISTIC theory of psychopathology interprets the individual as the unique product of complex interactions between biological, psychological, and sociocultural determinants. It makes little sense to ask how much of a given characteristic in a single individual is determined by heredity and how much by environment, since both are essential to the survival of the organism. However, it is still pertinent to ask what proportion of a given characteristic in a total population is determined by specific hereditary or environmental influences. Stated another way, the heritability of a trait is the proportion of the population variance that is determined by genetic endowment.
Much of the population variance with respect to many forms of psychopathology is believed to be acquired or learned as a consequence of adverse postnatal environmental experiences, often referred to as psychological trauma, stress, or deprivation. Freud considered that in adults with