People with depression often complain of a near-complete lack of energy. Not only do they experience mental fuzziness, but also physical tiredness. Researchers haven’t pinpointed why depression can trigger fatigue, but it is a key physical symptom.
Chronic headaches and unexplained back pain can be a symptom of depression. It might cause pain because the neurotransmitters responsible for relaying pain sensations to the brain are the same substances that regulate mood.
One of the classic signs of depression is sleep disturbance. You might wake up in the middle of the night and can’t get back to sleep or you sleep 10 to 12 hours each night and still want an afternoon nap.
Depression can cause major immune system issues. People who are depressed often have elevated levels of stress hormones. These cause inflammation, which triggers an immune system response.
People with depression may have frequent stomach problems, like nausea, bloating, diarrhea, or constipation. One possible explanation involves a neurotransmitter in the brain and gut called serotonin.