Are the Brown and Harris "vulnerability factors" risk factors for depression?

The Brown and Harris model of depression holds that certain "vulnerability factors"--namely early maternal loss, lack of a confiding relationship, greater than three children under the age of 14 at home and unemployment--can interact with "provoking agents" to increase the risk of depression. The validity of this model has been widely debated, with most of the discussion concerning the interactive nature of the model. There has been relatively little attention paid to the possibility that the "vulnerability factors" may be risk factors for depression. The purpose of this paper is to determine whether the four Brown and Harris "vulnerability factors" are associated with an elevated risk of depression, irrespective of whether they may interact with provoking agents. The analysis contained in this paper utilizes power analyses and confidence intervals. The findings suggest that the lack of a confiding relationship is strongly associated with depression, and that all four of the "vulnerability factors" may be associated with an increased risk of depression.