Post-Lyme syndrome and chronic fatigue syndrome. Neuropsychiatric similarities and differences.

BACKGROUND: Patients with chronic fatigue syndrome (CFS) and post-Lyme syndrome (PLS) share many features, including symptoms of severe fatigue and cognitive difficulty.
OBJECTIVE: To examine the neuropsychiatric differences in these disorders to enhance understanding of how mood, fatigue, and cognitive performance interrelate in chronic illness.
METHODS: Twenty-five patients with CFS, 38 patients with PLS, and 56 healthy controls participated in the study. Patients with CFS met 1994 criteria for CFS and lacked histories suggestive of Lyme disease. Patients with PLS were seropositive for Lyme disease, had met the Centers for Disease Control and Prevention criteria, or had histories strongly suggestive of Lyme disease and were experiencing severe fatigue that continued 6 months or more following completion of antibiotic treatment for Lyme disease. All subjects completed self-report measures of somatic symptoms and mood disturbance and underwent neuropsychological testing. All patients also underwent a structured psychiatric interview.
RESULTS: Patients with CFS and PLS were similar in several somatic symptoms and in psychiatric profile. Patients with CFS reported more flulike symptoms than patients with PLS. Patients with PLS but not patients with CFS performed significantly worse than controls on tests of attention, verbal memory, verbal fluency, and motor speed. Patients with PLS without a premorbid history of psychiatric illness did relatively worse on cognitive tests than patients with PLS with premorbid psychiatric illness compared with healthy controls.
CONCLUSIONS: Despite symptom overlap, patients with PLS show greater cognitive deficits than patients with CFS compared with healthy controls. This is particularly apparent among patients with PLS who lack premorbid psychiatric illness.