People have been experimenting with hallucinogenic substances for about as long as recorded history has been around. These drugs are currently experiencing resurgence: the use of hallucinogens on college campuses has grown in recent years, and drug companies have also taken a keen interest in them lately as they look to expand their repertoire of psychological medications.

Different types of hallucinogenic drugs

Defining a hallucinogen isn’t as straightforward as it seems, since a number of drugs can seemingly produce hallucinogenic effects. Marijuana, for example, can sometimes cause people to hallucinate or experience altered sensory perception, yet it isn’t classified as a hallucinogen. So there’s a lively debate about exactly how to classify different substances. That said, here is a list of drugs generally considered to be hallucinogenic:

  • Peyote
  • Mescaline (derived from peyote)
  • Mandrake roots
  • LSD
  • PCP
  • Psilocybin (Mushrooms)
  • MDMA (aka ecstasy; a cross between a hallucinogen and a stimulant)
  • DMT
  • Foxy
  • Nutmeg
  • DOM
  • Ketamine *MDA
  • Salvia divinorum

 

Some of these compounds are derived from natural substances, others from synthetic chemicals. While each substance comes with its own unique health risks, and some are more damaging than others, there’s no evidence that “natural” trips are any more or less rewarding or harmful than synthetic ones.

The effects of hallucinogens

Hallucinogenic drugs can produce a variety of altered sensory experiences. The following list of experiences was derived from LSD, but it can pretty much be applied to any type of hallucinogenic drug:

  • Time distortion or an altered sense of time
  • Animation of inanimate objects
  • Body dysmorphia (Seeing your hand as flat or stretched out, or the sense that you are not in your own body)
  • Mixed sensory perception,. such as seeing sounds or hearing colors
  • Shifting geometrical patterns or shapes
  • The emergence of hidden fears or suppressed anxieties
  • Out-of-body experiences
  • A sense that one can float or fly
  • A loss of identity or blending of a person with the objects & people around them.
  • A sense of brilliance or creativity
  • Especially vivid & sensory-rich experiences.

 

How hallucinogenic drugs work in the brain

For the longest time people thought that hallucinogens worked by increasing brain activity in various regions, which is understandable given the rich sensory experiences people feel while under their influence. Yet recent research suggests precisely the opposite is true: hallucinogens seem to work by reducing activity in parts of the brain that normally act as control centers to integrate information from all the different brain regions. As a result of this reduced integration, these “lower” brain regions are allowed to steal the show, producing a more raw, fragmented, sensory-rich experience

For example, fMRI brain scans of people under the influence of psilocybin found that the hallucinogen decreased hemodynamic activity, including blood flow, in selected regions of the brain such as the thalamus, the medial prefrontal cortex (mPFC), the ACC and the posterior cigulate cortex (PCC). Activity in these brain regions dropped by up to 20% relative to what it was before the injection. (Carhart-Harris et al., 2012)

“What is intriguing is that the regions that show the strongest reduction in activity are among the most heavily interconnected in the brain,” notes Christof Koch. “They act like traffic circles or hubs that link disparate regions. Thus, the brain on psilocybin becomes more disconnected, more fragmented, which might explain some of the dissociative aspects of acid trips.” (Koch, 2012, p. 19)