A few applications à 15 min with a mercury high pressure lamp with a good reflector and you look like you went to the Caribbean for holidays. Maybe add a filter for UV-C, but there is no ionizing radiation. Just show any lamp in question to your favorite dermatologist. If he seems unhappy, you have the chosen the right lamp.
Jokes aside, skin is very photo-active and I do think lamps can help greatly against these kind deficiencies.
Most lamps emit a line spectrum though, so it is not like real sunlight. I wonder if that is the reason people going to solaria often seem to have weird skin tones. Ask a dermatologist and don't forget eye protection.
Apart from that it has the same side effects as sun exposure. Too much leads to skin aging, sunburn, cancer, etc.
Those side effects can be mitigated or at least reduced by adding extra infrared or red light. Eg sunburns are prevented or greatly reduced by treating with near infrared either before or after UV exposure.
