Evaluating the inter-relationships among depression, anxiety and somatic symptoms in haemodialysis patients: a cross-sectional structural equation modelling study

BACKGROUND: Somatic symptoms frequently occur in haemodialysis patients, whereas depression and anxiety are also common but are often under-recognised issues. This study aims to examine the associations among depression, anxiety and somatic symptoms in haemodialysis patients. These symptoms may be linked together under a general distress construct in haemodialysis patients. METHODS: We surveyed 1085 dialysis patients between 1 March 2018 and 28 February 2023 at 17 dialysis facilities in Northeast Ohio with the 9-item Patient Health Questionnaire (PHQ-9), 7-item Generalized Anxiety Disorder and Kidney Disease Quality of Life instrument somatic questions. To evaluate associations across these multi-item questionnaires, we used latent variables and a structural equation modelling approach. We first compared single-factor, two-factor and three-factor models. We next considered bifactor and higher order factor models. We controlled for race, gender and age in all models. RESULTS: Our study sample included a high percentage of black patients (75%) and 150 (14.3%) survey participants screened positive for depression (PHQ-9 ≥10). All models fit relatively well, with the three-factor model fitting slightly better than the single and two-factor models. In the three-factor model, the associations for depression and anxiety (r=0.818), depression and somatic (r=0.800) and anxiety and somatic (r=0.784) were all high, potentially indicative of poor discriminant validity. We found that the bifactor model fit the best of the five models tested (comparative fit index=0.957, Tucker-Lewis fit index=0.959, root mean square error of approximation=0.043) and was the most substantively meaningful, with an overall internalising construct and specific domains explaining additional covariance across the questions. Being black (vs all other races), male (vs female) and older age all had significantly (p<0.05) lower levels of reported symptoms on most constructs. CONCLUSION: We found very strong associations among depression, anxiety and somatic symptoms in our sample of haemodialysis patients. All questionnaire items may be linked together under a common general distress disorder, while each still retains unique features of depression, anxiety and somatic symptoms not fully explained by internalising processes. Patient care approaches should generally consider screening for all three together, rather than only one.