Thanissaro Bhikkhu is the abbot of Metta Forest Monastery near San Diego, Calif., and has lived as an ordained monk in the Thai forest tradition of Buddhism for 24 years. He spoke with Beliefnet's Buddhism producer, Mary Talbot. Some people see drug experiences as spiritual experiences in that they open up new pathways in the mind. But at the same time, others are being closed down. What gets closed down varies from person to person, but usually it's mindfulness that goes.
People confuse mindfulness and alertness.
You're wowed by things that aren't actually all that substantial. There's nothing to guarantee that the realizations you get during drug use are valid. The Buddha saw that intoxicants of whatever variety limit brain function and give you strong states of delusion. When you're intoxicated, it's difficult to see reality for what it is. Not that you can't have moments of insight and intense experiences, but you don't realize how limited they are.