BackgroundThe Beck Depression Inventory (BDI-II) may be used to evaluate individuals for symptoms of depression. MethodsIn a 1-year prospective study, 52 adult Lyme disease patients with erythema migrans and 104 matched control subjects were clinically assessed and completed the BDI-II at study entry and approximately 6 and 12 months later following antibiotic treatment. ResultsThe mean BDI-II score was significantly higher at the baseline visit among Lyme disease patients compared with controls (P = .002), but no significant differences between the groups were observed at either the 6- or 12-month study visits. Over the course of the study, the mean BDI-II scores decreased an average of approximately 0.22 points per month (P < .0005) for Lyme disease patients, whereas the mean scores changed very little for controls (mean change = −0.02 per month, P = .50). The total number of somatic symptoms, of the 12 symptoms evaluated, strongly and directly correlated with the BDI-II scores at the baseline visit for the Lyme disease patients. ConclusionsThe mean BDI-II scores of patients with early Lyme disease significantly exceeded that of matched controls at study entry, but by 6 months the values did not differ significantly. There was a good-to-excellent direct correlation between the BDI-II score and the total number of symptoms, suggesting that the BDI-II scores were reflecting somatic rather than affective depressive symptoms. When using the BDI-II as an assessment tool of patients with Lyme disease, infection-related somatic symptoms per se need to be considered in the interpretation of the results.