Last year, I made a post advocating 3mg melatonin nightly as a way to relieve GERD pain. After a very negative personal experience with this treatment, I wanted to make a post to clearly warn everyone: DO NOT USE MELATONIN.
It can cause very serious autoimmune disorders. In my own case, it worked great for 8 months, but then I found out that it stimulated an autoimmune reaction in my body. My immune system is now attacking my thyroid, so in addition to taking Nexium for life, I will now be taking Synthroid (thyroid replacement) for life.
If you doubt the danger of melatonin, google "melatonin rheumatoid arthritis" or "melatonin crohn's" or "melatonin lupus" to find out all of the horrible diseases that melatonin has been known to worsen, and sometimes cause.
Please take this post to heart if you use melatonin for GERD or for other reasons. It's not worth it.