The only positive effect of tanning that has been established so far, and agreed upon by scientists, is the cosmetic benefit. A tanned skin looks better, and looks healthier, than an untanned skin. What has not yet been established, but what is generally suspected, is that when you look good you also feel good, and there is plenty of anecdotal evidence for this. Thus it is pretty well accepted that there may be psychological benefits of tanning, but they have not been measured yet. These benefits may turn out to be considerable, as feeling good becomes more and more accepted as being necessary for good physical health, and this concept of wellness is more widely relied upon by medical professionals.
There are positive side effects of tanning, of course, such as Vitamin D production, which is very important for health, but these benefits can be obtained at far lower doses of UV light than are required to get a tan – perhaps one-fiftieth of a tanning session will be enough. There can also be beneficial side effects of the waste heat (Infrared radiation) produced by sunbeds, which may have an effect on joint mobility and certain forms of arthritis. Beyond this, there are extensive medical benefits of UV light, but these can only be claimed by qualified medical practitioners.
UV light is used by dermatologists, for instance, in the treatment of psoriasis, eczema and certain forms of acne.