to adversity and the development of depression in adolescence or adulthood. One research strategy studies associations between a single specific experience, such as sexual abuse or physical or emotional maltreatment, and depression. There is ample evidence from mostly retrospective community and clinical studies of a significant association between childhood sexual or physical abuse and adult depression particularly among women (e.g., Brown et al., 1999; Kendler et al., 2000; MacMillan et al., 2001) and similar results from prospective studies (e.g., Bifulco et al., 1998; Brown and Harris, 1993). Some studies suggest that abuse experiences are especially predictive of chronic or recurrent depression (Bifulco et al., 2002a; Lizardi et al., 1995). However, several studies suggest that physical and sexual abuse are related to diverse adult psychological disorders, not specifically to depression. Many of the studies have not distinguished among the specific types of abuse, nor have they controlled for factors in the environment that are correlated with abuse, which could themselves influence the likelihood of depression (such as parental psychopathology). In a large study of psychiatric outpatients, Gibb, Butler, and Beck (2003) found that childhood emotional abuse was most specifically related to depression compared with sexual or physical abuse (see also Alloy et al., 2006).
Using a different research strategy, Kessler and Magee (1993) examined associations among one or more from a diverse list of adverse experiences and depression. Their large-scale retrospective epidemiological study of community residents who met criteria for major depression found that several childhood adversities (parental drinking, parental mental illness, family violence, parental marital problems, death of mother or father, and lack of a close relationship with an adult) were predictive of later onset of depression. Three early adversities—parental mental illness, violence, and parental divorce—were significantly predictive of recurrence of depression. In a later similar study, Kessler, Davis, and Kendler (1997), examining 26 adversities occurring by age 16, found that although many of the events were associated with adult major depressive disorder, the adversities were also related to a broad array of psychological disorders besides depression. The investigators also noted that exposure to one or more adversities is common, occurring to three-fourths of respondents, and that the adversities tend to overlap or cluster with each other. Furthermore, they noted that no claim to causal relationships between adversity and disorders is possible, since there may be unmeasured common variables responsible for both adversity exposure and later disorder. Thus, while childhood traumas and early stressful conditions may contribute to depression, more study of the complex pathways is needed.
The mechanisms by which specific childhood stressors, such as physical or sexual abuse, have their effects on later depression are not known directly. However, such experiences are highly likely to occur in the context