I believe the "drugs kill brain cells" claim was based on faulty research that has since been exposed.
Taking most drugs is perfectly safe and, in some cases, far less harmful than a lot of the junk food many people indulge in. Just stay away from the harder stuff, such as meth and heroin, which can actually cause you serious problems.
The safest drug on the planet is marijuana (this claim is supported by fact, not bias) and the safest way to ingest it is with a vaporizer. It should be noted, however, that you can become "psychologically addicted" to anything that makes you feel good, whether it is a drug or not.
Always exercise extreme caution when putting a new substance into your body. Gather as much information as you can so you can make an unbiased, informed decision. Make sure that the drug you intend to take is physically and, more importantly, psychologically compatible with you.
Good luck, friend.