Heavy smokers are more likely to report this symptom. The irritability people experience after quitting is caused by the body's craving for nicotine. Irritability associated with quitting will lessen over time. Nicotine is a stimulant, so it is not surprising that quitting smoking causes fatigue.
Heavy smokers are more likely to feel tired after quitting.
Fatigue occurs in the afternoon from 2pm - 4pm. Try nicotine gum, nicotine patch, take naps or a brisk walk. Nicotine affects brain wave functioning and may influence sleep patterns. It is not uncommon in the first few days after quitting for the ex-smoker to wake up frequently during the night. Dreaming about smoking is also common.