Biosocial Interactions
Not only are multiple distinct factors implicated in the genesis of a disorder, the profile of factors often conspires to lead to psychopathologic outcomes. Empirically, this profile is the statistical interaction between factors (in contrast with the main effects of factors). Thus a causal factor might operate only when it occurs in concert with another factor. For example, the experience of parental rejection early in life is a contributing factor in the development of conduct disorder but only among that subgroup of children who also display a biologically based problem such as health difficulties at the time of birth. Likewise, health problems at birth do not inevitably lead to conduct disorder; the interaction of a biologically based predisposition with a psychosocial stressor is often required for a psychopathologic outcome.
Another example is the known effect of chronic social rejection by peers in early elementary school on the development of aggressive conduct problems. This social stressor leads to conduct problems only among that subgroup of children predisposed toward externalizing disorders prior to experiencing social rejection. Among the subgroup not predisposed, social rejection does not result in conduct problems. Of course, the experience of social rejection might well incite another disorder (such as a mood disorder), again, if a predisposition to such a disorder exists.
The importance of biosocial interactions suggests the importance of examining multiple diverse factors simultaneously, both in empirical research and clinical practice.
