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Abstract: Objective: This study examined if associations between body mass index (BMI) and mental and physical health were independent of genetic and familial factors. Method: Data from 2831 twins (66% female) were used in an epidemiological co-twin control design with measures of BMI and mental and physical health outcomes. Generalized estimating equation regressions assessed relationships between BMI and health outcomes controlling for interdependency among twins and demographics. Within-pair regression analyses examined the association of BMI with health outcomes controlling for genetic and familial influences. Results: Adjusted analyses with individual twins found associations in women between BMI and perceived stress (P=.01) and depression (P=.002), and the link between BMI and depression (P=.03) was significant in men. All physical health outcomes were significantly related to BMI. Once genetic and familial factors were taken into account, mental health outcomes were no longer significantly associated with BMI. BMI in women remained related to ratings of physical health (P=.01) and body pain (P=.004), independent of genetic and familial influences. Conclusion: These findings suggest that genetic and familial factors may account for the relationship between increased weight and poor mental health. [Copyright &y& Elsevier]

Abstract: Objective: 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. Method: 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. Results: 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). Conclusion: 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. [Copyright &y& Elsevier]