Hi Strawberry- what a timely question. I have been wanting a salt lamp as well and I am hoping Santa (a.k.a. my husband) gets the hint after telling him to look at my Amazon wish list.
Also, I had wondering the same thing, specifically if anyone notices a benefit from the lamps. From a personal non- scientific experience, I feel markedly better when I am near the ocean. It is decidedly NOT an "aaaahhhhhh so relaxed love the beach, surf, sun" etc. because I used to avoid beach-type holidays like the plague. because heat and humidity make me feel like hell. Dysautomia issues big time. I mentioned the fact that oddly I seemed to feel better around salt waters to a few people who said something along the lines of "oh that does not surprise me, negative ions are said to make people feel better."
Although, I do not have an answer for you I can offer my final thoughts.....what the heck, the lamps are interesting looking, produce a pretty orange-golden light and if you get one do a little online price checking, fairly affordable. The prices seem to vary wildly. I found one website that sells all kinds of salt products and they make wild claims about the curative properties of salt, you feel like if you purchase something from them you have been brain washed into drinking the Kool-Aid. And of course the prices are much higher although it looks like the sell the exact products offered elsewhere for less money and less hype.
I'll let you know of my experience, assuming Santa comes through for me.
Take care, and thank you for asking a great question!
Cassandra