Mechanisms for the association of psychosocial characteristics with poor pregnancy outcome can be theorized
to occur by both direct and indirect causal pathways. For example, periods of stress can precipitate the release of
catecholamines, resulting in vasoconstriction and subsequently oxygen and calorie reduction to the fetus. Indirectly, psychosocial factors such as depression, anxiety, and low self-esteem have been shown to be associated with higher incidences of maladaptive health behaviors. In this study a score indicating a poor overall psychosocial state was significantly associated with smoking and drug use.