- **Sleep Disorders**: Insomnia, sleep apnea, restless legs syndrome, narcolepsy.
- **Chronic Illnesses**: Diabetes, heart disease, chronic kidney disease, liver disease, cancer.
- **Infections**: Viral infections (e.g., flu, mononucleosis), bacterial infections, chronic infections (e.g., HIV/AIDS, tuberculosis).
- **Endocrine Disorders**: Hypothyroidism, adrenal insufficiency, diabetes.
- **Nutritional Deficiencies**: Anemia (iron deficiency), vitamin B12 deficiency, folate deficiency.
- **Medications**: Side effects of drugs (e.g., antihistamines, antidepressants, blood pressure medications).
Pain - : Chronic pain conditions (e.g., fibromyalgia, arthritis).