A reader asks:

 Several of my siblings suffered with severe cases of infectious mononucleosis. They all experienced delayed sleep phase, but this symptom of mono seems to be absent from the medical literature! My siblings recovered normal sleep habits after their bouts with mono, but for myself, the delayed sleep phase problem has become chronic. Any comments and suggestions


Hypersomnia — abnormally long sleep — is common during the active phase of bacterial and viral infections. Delayed sleep phase is another matter: sleep duration is normal, or somewhat longer than normal, but both sleep onset and wake-up times are significantly later than normal. In such cases, light therapy starting at spontaneous (late) wake-up time, and edging earlier over days, may help to alleviate the sleep problem and also increase daytime energy. Once the infection has passed — as you have described for yourself — the prognosis of normalized sleep timing with light therapy is excellent. One caveat: during the active period of infection, the eyes may become hypersensitive to bright light, making the treatment difficult to tolerate. In such cases, dawn simulation may be the answer, but this has yet to be tested.