MDMA is also addictive, because it makes you feel good (it's not called "ecstasy" for nothing), and builds tolerance rapidly, so you need to keep increasing the dose. No, it's nowhere near as dangerous as meth/heroin/cocaine, but I have seen people spiral into pretty dangerous usage patterns, including switching to harder drugs when ecstasy isn't cutting it any more and they're stuck in a multi-day depressive withdrawal slump.

For all practical purposes, none of this applies to LSD, since trips are much more intense and unpredictable. Although there is a small subset of psychonauts who adopt an extreme sports mindset and intentionally push the envelope by taking larger and larger doses.