Interstitial cystitis/painful bladder syndrome (IC/PBS) is a chronic pain condition with unclear underlying etiology. Our objectives were to determine whether psychological distress was higher in twins with urological symptoms commonly found in IC/PBS than in twins without, and if so, did familial influences contribute to this association.

Data from 1165 female twins in a community-based sample were used. Urological symptoms, symptoms of posttraumatic stress disorder (PTSD), depression, anxiety and perceived stress were assessed with standardized questionnaires. Generalized estimating equation (GEE) regression models were used to examine the relationship between psychological distress and urological symptoms.

Compared to unaffected twins, twins with urological symptoms were more likely to report PTSD symptoms (OR=3.9; 95% CI=2.6–5.8), depression (OR=3.1; 95% CI=2.0–5.0), anxiety (OR=3.4; 95% CI=2.3–5.2) and perceived stress (OR=3.2; 95% CI=2.1–4.9). After adjusting for familial influences, the within-pair effects remained significant for PTSD symptoms (OR=2.2; 95% CI=1.2–3.8) and perceived stress (OR=2.2; 95% CI=1.2–3.8).

Familial influences partially explained the relationship between indicators of psychological distress and urological symptoms. Future research should examine shared environmental and genetic mechanisms that may further explain this relationship and improve diagnosis and treatment of this unexplained clinical condition.