http://news.bbc.co.uk/1/hi/magazine/4692359.stm

Dr Russell Newcombe, senior lecturer in drug use and addiction at Liverpool John Moores University:

"There has always been an underlying interest in alternative experiences and states of consciousness but that has risen a lot more in the past 10 years or so," he says.

"It goes with that whole section of our youth culture today which is interested in getting experiences, travelling the world and doing risky sports.

"On the other side of the coin there is a need for mystical and spiritual experiences to offset people's secular lives."

The effects, and drawbacks such as paranoia, vary but when a trip is particularly intense, users report a loss of ego or a renewed sense of their place in the universe."