In the Student Union bathroom at my college there was a smear of graffiti created from the inversion of one of the day's popular anti-drug slogans: "Reality exists for those who can't handle drugs." It was a joke that reflected some pretty serious team spirit and spoke to the divide between kids who did drugs and those who didn't.
If the tree trunk of experimental drug use sprouted upward into two main branches, one might have been called heroin and the other LSD. Heavy use created the junkie and the acid burn-out, two very different brothers born of the same family. In time, the limbs of these two branches created a canopy of cross addiction typified by the tragic demise of many of the team's highest functioning players like Jim Morrison, Jimmy Hendrix and more recently Jerry Garcia (the J squad).
Those who recovered from heavy drug use (if one really ever fully recovers) often describe the journey as one fraught with ill logic and flawed thinking. For example, Eric Clapton (acid-user, junkie, alcoholic, prescription drug abuser and of course nicotine addict) described his initial attraction to drugs as a way to hot-wire or short circuit the spiritual journey that he hoped would result in the truly timeless works of artists he strove to emulate. In retrospect, it had just the opposite effect on his talents as an artist and nearly destroyed his family life, career and health.
Experience tends to teach that drugs at their best do not reward the user with anything sustainable but extract a huge cost for the glimpses of self knowledge and awareness they may offer. A great artist becomes great through work not drugs. The same is true for the spiritually enlightened or mature. Though there are shaman who incorporate hallucinogens in their rituals, they are integrated as a part of a much larger method and not as a replacement for the hard work associated with religious self knowledge and spiritual growth.
Drugs, like medicine, are toxins. Misused or mis-proportioned they are often lethal. One makes a poor argument to say they were desirous of spiritual enlightenment when they bought an unknown substance from an unknown supplier and trusted that it is was of the formula, quality and quantity that would help them achieve a nearly impossible to defined end result. There are very few if any short cuts to the secrets of "soul" but there are many, many dead ends.
Time reveals truth. The importance of the mentor, teacher, guardian, parent in the process of mental and physical development is indispensable. Learn from the shared experience of your elders and use that to navigate to new horizons. Sailors use charts to by-pass the submerged obstacles that stole the lives of their predecessors. Before one sets off on the path of drug use, it might be wise to read the biographies of the explores that went before. Much can be learned from their trials and tribulations and much pain and suffering avoided.