Cancer treatments can cause reduced blood counts, which may lead to anemia, a blood disorder that occurs when there is not enough hemoglobin in the blood. Hemoglobin is a substance in the red blood cells that enable the blood to transport oxygen through the body. When the blood can not transport enough oxygen to the body, fatigue can result. This is a common condition in general, but may happen after radiation therapy to the lymph nodes in the neck. Medications used to treat side effects such as nausea, pain, depression, anxiety and seizures can cause fatigue.
Research shows that chronic, severe pain increases fatigue.
Stress can worsen feelings of fatigue. Fatigue may result when patients try to maintain their normal daily routines and activities during treatments. Modification may be necessary in order to conserve energy. It may not be clear which started first. One way to sort this out is to try to understand your depressed feelings and how they affect your life.