The LDN Story low dose naltrexone documentary

Low dose naltrexone (LDN) means taking a dose of naltrexone that is up to one-tenth, or 10%, of the dose that is usually taken for opioid addiction. A low dose of naltrexone is approximately 4.5mg of naltrexone a day compared with the usual dosage of naltrexone for opioid addiction which is 50mg to 100mg a day.

Low dose naltrexone uses
Low dose naltrexone has been used to treat:

Autoimmune thyroid disorders
Cancer
Chronic fatigue syndrome
Chronic pain
Crohn’s disease
Fibromyalgia
Gulf War syndrome
Multiple sclerosis
Myalgic encephalomyelitis.
Using low dose naltrexone for these conditions is “off-label” (which means it hasn't been approved by the FDA but it is still a recognized use).

There actually haven't been many big trials at all investigating low dose naltrexone, but the benefits of low dose naltrexone became apparent when people on a tapering schedule of naltrexone reported improvement in pain and fatigue symptoms with lower dosages of naltrexone rather than higher dosages. Small trials have shown that low dose naltrexone is beneficial for some conditions such as fibromyalgia, Crohn's disease, and pain.