Predictions and associations of fatigue syndromes and mood disorders that occur after infectious mononucleosis

Background Certain infections can trigger chronic fatigue syndromes (CFS) i n a minority of people infected, but the reason is unknown. We describe som e factors that predict or are associated with prolonged fatigue after infec tious mononucleosis and contrast these factors with those that predicted mo od disorders after the same infection. Methods We prospectively studied a cohort of 250 primary-care patients with infectious mononucleosis or ordinary upper-respiratory-tract infections un til 6 months after clinical onset. We sought predictors of both acute and c hronic fatigue syndromes and mood disorders from clinical, laboratory, and psychosocial measures. Findings An empirically defined fatigue syndrome 6 months after onset, whic h excluded comorbid psychiatric disorders, was most reliably predicted by a positive Monospot test at onset (odds ratio 2.1 [95% CI 1.4-3.3]) and lowe r physical fitness (0.35 [0.15-0.8]). Cervical lymphadenopathy and initial bed rest were associated with, or predicted, a fatigue syndrome up to 2 mon ths after onset. By contrast, mood disorders were predicted by a premorbid psychiatric history (2.3 [1.4-3.9]), an emotional personality score (1.21 [ 1.11-1.35]), and social adversity (1.7 [1.0-2.9]). Definitions of CFS that included comorbid mood disorders were predicted by a mixture of those facto rs that predicted either the empirically defined fatigue syndrome or mood d isorders. Interpretation The predictors of a prolonged fatigue syndrome after an infe ction differ with both definition and time, depending particularly on the p resence or absence of comorbid mood disorders. The particular infection and its consequent immune reaction may have an early role, but physical decond itioning may also be important. By contrast, mood disorders are predicted b y factors that predict mood disorders in general.