Everything we see in a dream is produced from the latent impressions in the senses and the mind. Everything we see during waking is mostly colored with the latent impressions in the senses and the mind. Everything we see under the influence of psychedelics is just like a dream and is produced from the latent impressions in the senses and the mind. Sensory and mental experience enhancer drugs are widely used at present to give people new types of experiences not available in the world. But they are only revealing what is already in the senses and mind, although hidden at present. If these hidden impressions are brought again into experience, people acquire a nature that was previously hidden and unmanifest. It can be good, but it could also be disastrous. Without knowing the consequences, the consumption of such drugs is ignorance.
Sāñkhya philosophy tells us about how the worldly experience is created from an unconscious realm of guna, chitta, and karma. The chitta is a repository of past impressions. The guna is the collection of our likes and dislikes. The karma is the collection of reactions to the past deeds. By their combination, new experiences are created. If the chitta is purified, all likes are dislikes are constrained to a limited set of impressions. If the guna is purified, then all impressions are constrained to a limited set of likes and dislikes. Thus purification of chitta and guna is a spiritual practice.
The chitta, however, is a literally infinite repository of past impressions. These include our past life experiences. They remain hidden and unconscious. However, by different practices, they can be uncovered and manifest into the conscious realm. Psychiatrists try to uncover past hidden trauma during hypnosis. A person sometimes sees flashes of insight without any logical derivation from past experiences. People sometimes see images if they come to a new place and it suddenly seems familiar to them because there are latent impressions in the chitta manifest by contact to that place. Similarly, psychedelic drugs can force a hidden memory or impression from the chitta.
Our expereince is organized top-down like an inverted tree. Even if we see an apple, the vision is not coming directly from an apple to our eyes. It is rather passing through the deeper layers of the unconscious and conscious mental and sensory apparatus because of which the perception is always colored by previous impressions. Since the impressions are already latent, therefore, they can be manifest without an external trigger. Or, we can use an artificial trigger like a psychedelic drug to manifest it.
Everything, including a psychedelic drug, has its guna nature. Its effect on the chitta will also be in accordance with whatever is prominently associated with that guna in our chitta. Generally speaking, all drugs are tamasic in nature. What they manifest will also be generally tamasic. However, in rare cases, a tamasic impression may also be tied up with a sattvic lesson in life. For example, death is a tamasic experience. But during that time, there might be associated impressions that are sattvic in nature.
One might, for instance, realize during death that he has wasted his life in temporary activities and everything he achieved during his life is lost within a moment. If such a realization is attached to a death experience, then the consumption of the psychedelic drug will not just evoke a sad memory but a good realization along with it. While such good results are possible, the general effect is always tamasic in nature. Therefore, the consumption of drugs is generally very harmful to most people although in rare cases, it may be useful too. Both have to be understood before experiments.
Of course, there is one universally useful effect of such consumption that we become convinced of having had past lives. There is no other way of explaining the psychedelic experience if the mind was a blank slate at birth and everything it sees can at most be the result of present-life experiences. Thus most people going to psychedlic experiences come out convinced about the possibility of reincarnation, alternative places of living, and don’t treat the present life as the be-all and end-all of existence.
If psychedelic experiences are terminated after such a conviction, then there is a net gain and very little loss. But if one gets addicted to such consumption, then the long-term effects of psychedelic drugs can be very dangerous because it is constantly putting the mind in a state incompatible with the body. The general effect of that incompatibiltiy is that the body can become sick rather than being transformed by the mind and the person loses the capacity to achieve anything worthwhile in this life.