The findings of our detailed analysis are not easy to interpret, first of all, because other variables changing over the life cycle (like hormonal status, child care, social conditions) were not assessed. The fourfold interaction between sex, age, marital and employment status could not be analysed neither, because numbers would have become too small. Finally, marital status and employment status may act as factors influencing referral. Concerning the latter problem, it has to be stressed though, that we exclusively analysed first ever admissions from a strictly defined catchment area and that at the time period for which data were collected the psychiatric out-patient care system was underdeveloped in Vienna. If nothing else, our data can show what might happen to the sex ratios of incidence rates if marital and employment status were considered together with age.
With these caveats in mind, we can first confirm the finding by Jorm [1
] of an inverted U-shape of the female/male ratios of depression rates over the life cycle. While being around 1.5:1 both in young adulthood and around the age of 60, the female/male ratio increased towards mid-life, with a peak at 45 to 50 and declined thereafter. Thus, our data confirmed the results of other studies quoted in the introduction of the present paper [4
], showing that depression in women becomes less frequent after the menopause. Eaton et al. [18
] in an incidence study starting from ECA data also found an inverted U-shape for female depression rates.
The two interpretations which come immediately to one's mind are biological on the one hand (female rates are increasing during the hormonally active period of women and decrease thereafter) and psychosocial on the other hand (life stress is increasing for women with middle age and decreases thereafter), which might mutually influence each other. No decision, however, is possible between these interpretations without considering other variables.
When analysing the additional influence of marital status it becomes clear that it was marriage which largely accounted for the inverted U-shaped curve. In married persons the female/male ratios climbed early (at around 30) to the 3:1 level, stayed there until the age of fifty and declined sharply thereafter. In other words: among the married the inverted U was broad, while in the total population it was rather a V than an U.
Thus, while among the married, rates were usually lower than among the not married, the gender gap was larger at a much earlier age than in the total population. This favours a psychosocial interpretation (marriage being more stressful for women than for men), but still, a biological interpretation is not ruled out, since married women may rather have children -and child bearing is related to hormonal changes (there was no possibility in our analyses to find out how frequently post-partum depression occurred).
Among the not married (taken as a group, including the never married, the divorced and the widowed) the inverted U-shape curve was found only in a rudimentary form, with a decline after the age of 40 (from around 2.8:1 to 1:1 at the age of 50 and later). It is difficult to interpret this curve, also if considering that the subgroup of the never married corresponded to the total group of the not married (for divorced and widowed persons the analysis could not be carried out due to the small numbers of cases in these subgroups if divided into single age groups.)
Employment status also changed the general pattern of an inverted U-shape found for the total population to a substantial degree. Among the employed the female/male ratio was constant (below 2:1) from the age of 18 to 50, and dropped thereafter to 1:1. The inverted U-shape virtually disappeared in this analysis. It seems that up to the age of fifty the raised risk for employed women was not age-dependent on age; the female preponderance tended to disappear beyond the age of 50. The not employed showed a pattern which was the opposite to that observed in the total population – there is a U-curve – but not an inverted one, but an upright U, i.e. in midlife not employed men had a clearly higher risk than not employed women.
The employment findings clearly favour a psychosocial explanation of the variations of the female/male depression rates over the life cycle as opposed to a biological one. If men were not employed in midlife, the risk of being admitted for a first ever depression episode was much higher than that for women. Data support the hypothesis that unemployment increases the risk for psychological disturbances- especially for affective disorders – in both men and women [2
]. The reverse sex ratio found in the not employed group of our investigation may reflect differences in the demands and social role expectations connected to the specific social roles of men and women. Unemployment may undermine menus ability to fulfil their role obligations. For married men unemployment has additional implications for their family status and relationships. In this context, it has to be stressed that women's and men's labour market position and role in the family have undergone substantial changes since the 1970s and the impact of psychosocial mechanisms on both women and men might have changed during the last decades.
Our analyses show, that the female/male ratio in first ever admitted depressed patients was age dependent and that there is a complicated interaction with marital and employment status. As the presented data are cross-sectional, the age group differences could as well rather reflect cohort than ageing effects. While we cannot be sure whether these findings are relevant for the aetiology of depression or only reflect referral peculiarities, they suggest that incidence studies should be carried out in unselected community populations considering sex, age marital and employment status simultaneously. Only in doing so we can narrow down the number of possible psychosocial and biological explanations of the gender gap in depression.