Interstitial cystitis/painful bladder syndrome (IC/PBS) and depression are two diseases of chronic, unknown etiology and often occur concomitantly without a reasonable reason. Past studies have suggested that the prevalence of depression in IC/PBS patients ranges from 5 % to above 50 %. Some diseases have interaction with each other and therefore be co-existed. Similarly, there may also have interaction or causal effect between depression and IC/PBS. There are many different subtypes of depression with different severity or mechanism. The effect of comorbidity and interaction may therefore different among these subtypes. We hypothesized that depression is a risk factor of IC/PBS, and the effect was related to different type of depression. This study used a nationwide database with retrospective cohort study, and aimed to investigate the causal effect of different depression subtypes on IC/PBS.

Two types of newly diagnosed depression between 2002 and 2013 were identified from a nationwide database as the depression cohorts. Subjects which diagnosed of IC/PBS before depression were excluded. All depression patients were divided into two subgroups according to ICD-9 coding as Major depressive disorder, recurrent episode; and Major depressive disorder, single episode. These subjects were further matched one to one by confounding factors (including age, and other 12 comorbidities) with propensity scores as matched cohorts. All subjects were followed up during the study period to detect the event of IC/PBS. The hazard ratio (HR) of IC/PBS between depression and non-depression cohort in each type of depression was applied before and after matched by propensity scores. The duration of IC/PBS as consequence of depression and incidence density were calculated.

There were 21,646 depression and 607,535 depression subjects, respectively, including11,290 and 10,281 patients in recurrent type subgroup and single episode type subgroup, respectively. Each subgroup was matched one to one using propensity score for confounding factors and yielded 11,179, 10,220 depression and non-depression cohorts among two subgroups. Demographics, including age, sex and 12 comorbidities, were similar between two cohorts of the same subgroup. Subgroup with recurrent type of major depressive disorder had significant higher incidence density and shorter duration of developing IC/PBS than matched control. (6.929 per 10,000 person-years and 4.67±2.65 years). After adjusted, the risk of IC/PBS remained significantly increased in recurrent type of major depressive disorder, HR=1.54 (95% CI, 1.039-2.269; p=0.031).

After controlling the confounding factors in our cohort study, the risk of IC/PBS was significantly increased in patients with recurrent or severe depressive disorder. A cross-talk pathophysiology of depression and IC/BPS is possible. Further study to investigate the effects of other types of depression was suggested. This finding could imply valuable cues to a urological approach, and preventive measures for holistic care in depressive disorder patients. Early identification and treatment of depressive disorder were important for prevention of BPS/IC in these numerous and disabled patients.

The risk of IC/PBS was significantly increased in patients with recurrent or severe depressive disorder. Early identification and treatment of depressive disorder were  important for prevention of BPS/IC in these numerous and disabled patients.