among those aged 15-44 years (WHO, 2004), affecting approximately 14.8 million American adults, age 18 and older, in a given year (Kessler et al., 2005).
The public health significance of depressive disorders is enormous. The exact etiology of depression is still being intensely researched. Several factors including genetic, biological, psychological, and environmental issues could be involved in the development of depression (Lewinsohn et al., 1988). There is evidence to show that depression occurs with considerable frequency in childhood and adolescence (Costello et al., 1996); the gender difference in major depression usually manifests at mid-puberty that is, around 13 years of age (Goodwin et al., 2004) and persists through adult life (Piccinelli & Wilkinson, 2001). Studies have indicated consistent gender differences in depressive disorder. For instance, the prevalence of depressive disorders has been shown to be 1.5 to 2 times higher in women than in men, beginning in early adolescence (Weismann & Klerman, 1985; Kessler et al., 1993; Ayuso-Mateos et al., 2001; Vicente et al., 2004; Modabernia et al., 2008). Contrary to the above, Stordal et al. (2001) reported minimal gender differences. Many explanations have been put forth for the observed gender difference involving artifactual, psychosocial, genetic and endocrine causes. According to Piccinelli and Wilkinson (2001), while artifactual determinants may enhance female predominance somewhat, for the most part gender differences in depressive disorders are genuine. The authors did not find any genetic and biological factors to influence the manifestation of gender differences. Silverstein (2002) observed the prevalence of somatic depression (e.g., appetite and sleep disturbances, and fatigue) but not pure depression (that is, all the depression criteria minus the somatic criteria) to be much higher among women than men.