Aims/hypothesis: The aim of the study was to determine whether diabetic peripheral neuropathy (DPN) is a risk factor for depressive symptoms and examine the potential mechanisms for this relationship.
Methods: This longitudinal study (9 and 18 month follow-up) of 338 DPN patients (mean age 61 years; 71% male; 73% type 2 diabetes) examined the temporal relationships between DPN severity (mean +/- SD; neuropathy disability score [NDS], 7.4 +/- 2.2; mean vibration perception threshold, 41.5 +/- 9.5 V), DPN somatic experiences (symptoms and foot ulceration), DPN psychosocial consequences (restrictions in activities of daily living [ADL] and social self-perception) and the Hospital Anxiety and Depression subscale measuring depressive symptoms (HADS-D; mean 4.9 +/- 3.7).
Results: Controlling for baseline HADS-D and demographic/disease variables, NDS at baseline significantly predicted increased HADS-D over 18 months. This association was mediated by baseline unsteadiness, which was significantly associated with increased HADS-D. Baseline ADL restrictions significantly predicted increased HADS-D and partly mediated the association between baseline unsteadiness and change in HADS-D. Increased pain, unsteadiness and ADL restrictions from baseline to 9 months each significantly predicted increased HADS-D over 18 months. Change in social self-perception from baseline to 9 months significantly predicted increased HADS-D and partly mediated the relationships of change in unsteadiness and ADL restrictions with change in HADS-D.
Conclusions/interpretation: These results confirm that neuropathy is a risk factor for depressive symptoms because it generates pain and unsteadiness. Unsteadiness is the symptom with the strongest association with depression, and is linked to depressive symptoms by perceptions of diminished self-worth as a result of inability to perform social roles.