The UAB Neuroinflammation, Pain and Fatigue Lab is looking for individuals to take a low dose of naltrexone or a placebo for 6 months. Every participant will receive the drug at some point during the study. You will be asked to come in for a screening session; to complete a daily symptom questionnaire and to provide blood samples during the 6-month period. If eligible, you will be compensated up to $425. Participants must: Have moderate to severe chronic fatigue (for at least 12 months); Not be pregnant or currently planning to become pregnant; Be without any significant medical conditions such as heart disease; and Not currently using opioid medications. For more about this study, call (205) 530-8006.