By Sant Kirpal Singh, excerpt from the "Teachings of Kirpal Singh", Vol. II, page 64 - 65

It is amusing to note about the Opiates (LSD, Marijuana, etc.) for producing hallucinations. You may please note that spirituality is the science of the soul, and the soul is a conscious entity in the body. The way back to God as offered by the Masters is one of developing inner consciousness with the aid of Holy Naam (the Word). All suchlike outer aids, resulting in temporary hallucinations are certainly a mockery for the Divine Grace. You can well understand the vast difference between having a conscious and wide-awake approach for proceeding within and that which makes recourse to these outer aids, which are no less than opiates creating sensational vibrations. You will recall that the observance of a strict diet by avoiding all flesh food, intoxicants and opiates, is a basic essential for inner spiritual progress, for attaining a refined state of mind. We have to develop consciousness, the divine attribute of soul, and for the achievement of (inner) consciousness, inner and outer piety and chastity are very much needed. The drugs are equally harmful, and should be avoided, which dull the brain and cloud the mind with vague feelings of distrust and confusion. You are advised to convey this piece of right understanding to all the dear ones who are on the holy Path and to others who seek your counsel in this behalf.

Question: Do those who take drugs as LSD and have certain experiences – are they valid experiences?

No, no, they are hallucinations. That’s the death of the soul, you follow me? The consciousness is lessened, naturally they will have to go to the lower planes. That is all this intoxication starts, it is still more death to the soul. It is deterioration. Definitely going down to beastlihood. Even a snake is conscious but there are different degrees. Man's consciousness is more. If you use suchlike things your consciousness is affected. You will have to go to the lower planes. The so-called "spiritual experiences" had under the spell of drugs are misleading and are rather likely to affect your inner progress. Spirituality is a research into the realms of reality – the consciousness. Drugs, opiates and intoxicants should not be partaken as these will not only affect your health adversely but shall be detrimental for your spiritual progress. You should please leave off all such drugs and learn to live without their use.