Drug use has been traditionally employed for spiritual purposes and introspection for hundreds, thousands, of years, but the practice of drug use was carefully monitored and guided under an experienced and trained person, and these methods persist in some cultures, even today. Many anthropologists are guided in these experiences.
Using street drugs or other drugs without any spiritual discipline or guidance can be disastrous and impede growth or insight, but sometimes they will open a person's perception a bit and perhaps encourage them to keep searching and growing. Sometimes drug-induced mystical experiences can have the same effects as naturally occurring mystical experiences.
I have experienced many altered states of consciousness, in part because I am schizoaffective with a bi polar affective, in part from prayer and meditation, and also some drugs. I do not recommend drugs, especially if you are bi polar or have any other mood, mental, or thought disorder.
That being said, drugs, including alcohol, marijuana, and to a much lesser extent, ecstasy and others were a part of my experience, especially entering college, good or bad. By the time I started college, I had already been experiencing altered states and hallucinations naturally from childhood, so it is not surprising that explored some drugs as well.
I have written great papers and made high As while stoned, manic, sleep deprived, delirious, and any combination of the above. I have found marijuana useful in provoking thought and helping to get ideas onto paper. In fact, I've used marijuana to motivate myself to write papers for school.
However, drugs do not affect each person in the same way. The first time I smoked a large amount of marijuana, I had extremely rapid mood swings -- laughter, panic, laughter panic. My vision broke into a million tiny windows, and I fell through them, screaming.
Although marijuana initially seemed to provoke insight, and it did in some ways, I eventually found that the insights were not superior to those I have in a sober state, if I even have a sober state to begin with.
All of the major altered experiences I have had that led to insight, growth, transcendence, love, and healing occurred naturally without the use of drugs, most of them spontaneously. (I also, of course, cultivate spirituality through disciplined prayer and meditation.) In my own experience, while drugs have at times stimulated very insightful thoughts -- and helped me write great papers with top scores in my classes -- they are a short cut for the hard work of spiritual discipline. Even if you have a genuine mystical experience induced by drugs -- and this is definitely possible -- it will take meditation and discipline to actually integrate and live out this experience. In other words, however you have a mystical experience, spontaneously, drug-induced, from prayer or meditation, you must live it out or it will not be transformative, and without transformation, there is no spirituality.
My spontaneous experiences have been far, far more vivid, far more transformative and mystical than any drug-induced state I have ever experienced. I find that drugs bombard the ego. The disintegration or disorientation can be so quick and vivid that one cannot cope -- that was me screaming and screaming as I fell through the windows of my life, my ego fragmented and afraid.
On the other hand, meditation takes much longer to practice and enter into. Transformation occurs, but it is often subtle and gradual. During meditation, an epiphany may occur, but this is often after at least some practice. With time to adjust and practice, losing the ego is not so terrifying like it is on drugs. It occurs naturally.
In truth, all I have really learned from drugs is the same thing I learned from life while not on drugs -- that the ego is constantly changing. There is nothing permanent in here to grasp onto, to hold onto. It is all slipping away. This is true when sober or drugged. There is no greater truth in drugged states. The same truths are here, now, either way.
Coming to this truth is actually how I have learned to cope with my "disorder," which involves mood swings, disorientation, hallucinations, delusions, and delirium. I often go about my life, school, work, and social activities delirious and manic as hell and often somewhat psychotic. But in truth, the reality I perceive in those states is the same thing. There isn't anything greater there. No greater truth to be found.
By detaching from perception and living mindfully, a person can converse and go about life quite intelligently and competently while psychotic. My psychiatrist and therapist often seem to think I'm doing very well when I know I am hallucinating.
The trick is to see that the psychotic state and the "sober" or "sane" state are both illusions. Then they become one and the same, and when both states are one, I can navigate in one about as well as the other.
If a drug-induced state has opened your mind, that is wonderful. It really is, and there is nothing wrong with it, but abusing a drug to achieve this state will never work because these experiences are fleeting, whether drug-induced or naturally occurring. The true work of spirituality is applying the insights in daily life and being transformed in the process, letting go of the ego in detachment.
If you must use a drug to talk to God, you are attached to the drug and may be mistaking the drug for the mystery itself.
IF you are going to use drugs to explore the mind, you MUST do this as responsibly as you can, and you cannot neglect the discipline of meditation. You will get no where if you are not able to apply the insights in your daily life without drugs.