The side effects I got from using LDN seemed unusually severe and I have not heard of others getting what I got.........
The first time I tried it I found I could not tolerate it internally at all. I have a condition that mainstream medicine calls Non Ulcer Dyspepsia, and even a tiny drop of LDN hurt my stomach like hell. It was as if I had a drop of acid. I am now using some Omeprazole which modifies this problem somewhat, (as I get it with foods also) but I don't really want to be on Omeprazole long term due to its possible side effects.
I then went onto transdermal LDN, and was on that for a year. It didn't do much for my ME symptoms but did seem to work quite well as a mild antidepressant. I have since been in touch with someone who knows quite a bit about LDN and she told me that some research had been done on transdermal LDN and it was suggested that it is not acting on the endorphin blockage in the way that taking it internally would do.
I then had a gap of a year and tried again. This time I tried the sublingual version which was being produced by Dicksons Chemist in Scotland, where I had got my previous supplies from. Even sublingually, I guess a tiny drop can go down the stomach and I had the horrible burning pain I got from the oral kind.
Even worse, the neurological symptoms I got from LDN on the 2nd occasion (I didn't get this the first time) were horrendous. I was on 1ml sublingually, though I did drop it to 0.5 for a while and the symptoms were not quite so severe. I would repeatedly jerk awake each time I was dropping off to sleep, over and over. So it was not insomnia as people have described it, but my brain somehow produced this awful side effect. I had a horrible migraine not surprisingly from this.
I have never heard of anyone else getting this problem, but funnily enough am just reading a novel where a character gets exactly this side effect from morphine.
In retrospect I could have tried it in the daytime to get over this, but could not sort out the severe stomach pain issue.