If you have ever considered trying drugs only to have sex under their effect, then let me summarize what their effects are on your body. First of all, let me start with the most widely used one, marijuana. While it gives you a sense of euphoria, it also dries mucous membranes, including the mouth and the vagina, as well. So, keep in mind that oral sex, and sex with no lubrication can become painful, even though the euphoric feeling might suppress it.
If you go on to party drugs, including amphetamines and the like, date rape drugs, cocaine and ketamine and the likes, then you must know that their effects are varied. While amphetamines push you into a sense of euphoria, love and peace while stimulating your body and keeping you awake, date rape drugs make you feel as if you were extremely drunk, which can mean that the person who uses it does not simply pass out, but rather passes away. The latter category simply kills pain, so its effect on sex can be pretty much ignored.
Still, there are others with extreme effect on the sexual experience. In case of hallucinogens, such as LSD, Mescaline or Psylocybin, your perception changes, and you might feel closer to your partner mentally, but you might also experience severe, scary hallucinations, or lack of sleep.
Heroin will probably have a negative effect on your sex life, as the euphoric state it gives is so intense that you will no longer feel the need to have sex.
Besides, their effects on the psyche varies from person to person, so addiction might be the least severe mental disorder that they can cause.