Learn about HPPD

Causes of Hallucinogen Persisting Perception Disorder

The underlying cause or causes of HPPD are still unknown. There are multiple hypotheses and theories as to what the root of this disorder is, yet none are conclusive or definitive.

The prevailing theory suggests the occipital cortex and the non-dominant temporal lobe demonstrate disinhibition, and also greater spectral coherence. This disruption in coherence becomes systematic and affects neighboring regions in the brain similar is scope to pre-seizure activity specifically in the areas of the brain that process visual stimuli. Simply put, the brain can no longer translate light into images properly and although at present the damage appears to be irreversible, the NNRF is committed to finding a cure.

Another theory presented, is that the thalamocortical loop in an HPPD scenario recycles sensory information throughout the brain much longer than it should. This is a result of the failure of the GABA mediated inhibitory mechanism for prolonging this excessive feedback loop. To date, no neural imaging studies have been done to thoroughly scan and study the HPPD brain, however QEEGs definitively show a disruption in coherence as mentioned earlier. As there might be several neurotransmitter systems that might be affected within the thalamocortical loop, co-morbid conditions such as depersonalization, derealization and intensified anxiety are the result. Make no mistake, this is an acquired condition that must be studied and investigated in depth.

The onset of the HPPD is not necessarily the result of the abuse of hallucinogenic drugs as it can manifest in individuals after a single use. HPPD is understood to generally worsen with ongoing drug use, and improve with abstinence, although this is not consistent. There are many hallucinogenic and psychedelic drugs known to cause HPPD, with LSD by far being the most common culprit.



Drugs that are known to cause HPPD


    HPPD tracer symptoms.


  • PCP
  • DMT
  • 5-MeO-DMT
  • MDMA
  • MDA
  • 2C-E
  • 2C-I
  • CBD
  • Synthetic cannabinoids
  • Psilocybin (Magic Mushrooms)
  • Salvia Divinorum
  • Diphenhydramine
  • Zolpidem
  • Dextromethorphan
  • Eszopiclone
  • Diphenhydramine