In this face to face survey of 3010 South Australians self-reported urinary incontinence was found in 20.3% (n=610), depression in 15.2% (n=459) and both in 4.3% of respondents. Those with urinary incontinence and comorbid depression were more likely to be aged between 15 to 34 years and never married when compared to those with only incontinence. Multivariate analysis demonstrated that in those with urinary incontinence, an overall health status of Fair or Poor, or the perception that their incontinence was moderately or very serious, increased the risk of having comorbid depression. Depression had a marked effect on QOL for the general population and a significant, additive effect on those with incontinence. Respondents who reported that they experienced urinary incontinence with comorbid depression scored significantly lower than those experiencing incontinence without depression on all dimensions of the SF-36. The interaction between urinary incontinence and depression had a significant effect on the physical functioning dimensions of quality of life.
The quality of life of people who experience urinary incontinence with depression, in both adult females and males of all age groups, has not been assessed previously via population surveys using face to face interviews. Other studies have assessed this qualitatively, or have discussed stigma, and other problems associated with incontinence including depression. But how urinary incontinence and depression interact and affect QOL has not been considered [25–28]. A lack of population data prompted the retrospective analysis of an existing dataset, already available from the 1998 SAHOS, where questions regarding urinary incontinence, depression and quality of life were asked together. At the time of this study, the questions about urinary incontinence were not validated, however they reflected the definition used by the International Continence Society (ICS) . They have since been validated by other authors .
This study has several limitations. Firstly the symptoms of urinary incontinence were not clinically quantified. However, in a population study of this size, it would not be practical to clinically examine cases for this condition, and prevalence rates using self-report have been found to be similar and cost less compared to those found from diagnostic tests . Secondly because recall times differ for urinary incontinence, depression and the quality of life measures, it is possible, that depression and urinary incontinence did not co-exist when the survey was administered. However urinary incontinence and depression are relapsing and remitting conditions and it is difficult to examine the temporality and causality in a cross sectional study. Lastly the use of the PRIME MD in this study to determine depression deviates slightly from the original intentions of its authors , as the initial depression screening questions were not used, and the mood module was administered to all in the study. However the prevalences of urinary incontinence (20.3%)  and major (6.7%) or other (8.6%) depressive syndrome (15.2%)  are comparable with other studies. Circumstances where both these conditions occur together (20.5% of those with urinary incontinence) are also equivalent to international studies [3, 7].
Univariate analysis indicates that younger people, and those never married were more likely to experience depression when they had urinary incontinence. This is not unexpected, as incontinence is often considered a disease of older women who have had children, possibly a plausible explanation for their incontinence. In the above group, there may not be an explanation for the condition, leading to a state of low mood and depression.
In the multivariate analysis, self-reported Fair or Poor health, and the perception that one’s own urinary incontinence was moderately or very serious were strongly predictive of having incontinence with depression. This may indicate that one’s own perceptions of a condition, and their overall health may lead to an increased likelihood of experiencing mental illness. However as this study was cross sectional, we were unable to determine whether the depression was caused by incontinence, or a person’s depression increased their perception of symptom severity. This will be explored in future qualitative work.
In the quality of life analysis, we compared respondents with “Incontinence with depression” to those with “Incontinence without depression”. “Incontinence with depression” describes respondents who answered in the positive for any of the incontinence questions, and includes those who also scored positively for depression by the PRIME-MD. “Incontinence without depression” includes respondents with urinary incontinence, not diagnosed with depression by the PRIME-MD in this survey. Respondents with urinary incontinence and depression scored significantly lower on all dimensions of the SF 36, with depression scoring lower than urinary incontinence and those with both conditions together scoring lowest of all. When these conditions occur together, there was a major additive effect particularly in the Mental Health scales, greater than that with either condition alone. It appears that depression increases a person’s negative perceptions of their physical symptoms (incontinence) reducing their QOL scores further than would be expected if either condition occurred independently. This effect is also reflected in the interaction between incontinence and depression and its impact on the QOL dimensions that measure physical functioning.
It may be that identifying and treating depression in a person with urinary incontinence, a patient’s mental health (QOL) will not only improve but also, indirectly their physical QOL.