Effect Index, which is currently under construction, is a resource dedicated to establishing the field of formalised subjective effect documentation. It is the home of the Subjective Effect Index (SEI), which exists to serve as a comprehensive map of all potential experiences which can occur under the influence of any class of psychoactive compound, particularly hallucinogens.

The effects identified here are accompanied by detailed descriptions of how it feels to experience them. These are written in an objective and consistent writing style which is based upon phenomenological observation and avoids the use of metaphor or analogy. The descriptions also strive to use language which is as simple and understandable as possible; this has been done in the hope that they will serve as a universal terminology which allows people to describe and discuss that which was previously considered ineffable.

The effects are separated into over 200 distinct components which are organised into categories based on the sense affected and their behaviour. Many of these are further broken down into levels, subcomponents, and variations in style which can occur across different substances. Detailed replications are included whenever possible to supplement the text descriptions in the form of images, audio clips, and animations.

Cognitive effects




psychological states

Transpersonal states

Physical effects (coming soon!)



  • Appetite suppression
  • Cough suppression
  • Decreased libido
  • Motor control loss
  • Nausea suppression
  • Orgasm suppression
  • Pain relief
  • Respiratory depression
  • Sedation
  • Seizure suppression


  • Bodily pressures
  • Bronchodilation
  • Changes in felt bodily form
  • Changes in felt gravity
  • Excessive yawning
  • Gustatory hallucinations
  • Mouth numbing
  • Muscle relaxation
  • Muscle tension
  • Muscle tremors
  • Olfactory hallucinations
  • Optical sliding
  • Perception of bodily heaviness
  • Perception of bodily lightness
  • Photophobia
  • Physical autonomy
  • Physical euphoria
  • Pupil constriction
  • Pupil dilation
  • Spontaneous physical sensations
  • Watery eyes

Uncomfortable side effects


  • Abnormal heartbeat
  • Decreased heart rate
  • Decreased blood pressure
  • Increased blood pressure
  • Increased heart rate


  • Brain zaps
  • Dizziness
  • Headaches
  • Increased bodily temperature
  • Seizure
  • Temperature regulation suppression


  • Constipation
  • Dehydration
  • Diarrhea
  • Difficulty urinating
  • Dry mouth
  • Frequent urination
  • Increased perspiration
  • Itchiness
  • Muscle contractions
  • Muscle cramps
  • Muscle spasms
  • Nausea
  • Physical fatigue
  • Restless legs
  • Runny nose
  • Salivation
  • Skin flushing
  • Stomach bloating
  • Stomach cramps
  • Teeth grinding
  • Temporary erectile dysfunction
  • Vasoconstriction
  • Vasodilation


  • Psychedelics
    • Visual effects of the psychedelic experience
    • Cognitive effects of the psychedelic experience
    • Miscellaneous effects of the psychedelic experience
  • Dissociatives
  • Deliriants