The hallucinations and perceptual changes consist of, but are not limited to, visual snow, trails and after images (palinopsia), light fractals on flat surfaces, intensified colors, altered motion perception, pareidolia, micropsia, and macropsia.

In 1898, the English physician and intellectual Havelock Ellis reported a heightened sensitivity to what he described as "the more delicate phenomena of light and shade and color" for a prolonged period of time after he was exposed to the hallucinogenic drug mescaline.

LSD therapist Stanislav Grof noted an HPPD phenomenon in his book LSD Psychotherapy from 1978, which noted that "[l]ong after the pharmacological effect of the drug has subsided, the patient may still report anomalies in color-perception, blurred vision, after-images, spontaneous imagery, alterations in body image, intensification of hearing, ringing in the ears, or various strange physical feelings."

There are individuals who have never used a drug which could have caused the onset, but yet experience the same grainy vision reported by those with HPPD, like people with the closely-linked neurological disorder known as visual snow syndrome.

[19] Visual snow syndrome is defined as lacking any known cause and is specifically distinguished from HPPD in its nosology, yet further research may clarify the relationship.

[1] Anxiety, PTSD [20][21] and panic[22] can promote depersonalization-derealization[23] and visual disturbances, and vice versa, so these features may run in multidirectional relationships.

Abraham suggested that all three can arise from a broader mechanism of disinhibition in sensory perception, affect and sense-of-self occasioned by psychedelic experience.

[7] A vast list of psychoactive substances has been identified and linked with the development of this condition, including lysergamides like LSD and LSA, tryptamines like psilocybin and DMT, phenethylamines like 2C-B, MDMA, MDA and mescaline.

It also seems that combining recreational or medical drugs that act on the 5HT2-a receptors, like SSRIs, drastically increases the chances of developing HPPD due to the drug-drug interaction.

[26] HPPD is not related to psychosis due to the fact people affected by the disorder can easily distinguish their visual disturbances from reality.

The primary neurobiological hypothesis is that persistent hallucinations are the result of chronic disinhibition of visual processors and subsequent dysfunction in the central nervous system following consumption of hallucinogens.

On a macroscopic level, the lateral geniculate nucleus (LGN) of the thalamus, which is important in visual processing, has also been implicated in the pathophysiology of HPPD.

[citation needed] Being a drug-related disorder, HPPD is therefore vulnerable to internalized anti-drug stigma, specifically around 'flashbacks' and 'brain frying', which were heavily propagandized in prohibitionist campaigns in the 20th-century.

[citation needed] Antipsychotics such as aripiprazole or risperidone, intended to treat mental disorders like schizophrenia, should only be taken in careful consultation with a psychiatrist experienced in HPPD.

Two young men with HPPD and schizophrenia as a comorbidity experienced a remission of visual perceptual disturbance during a 6-month follow-up observation under treatment with risperidone.

Case reports of psychotherapy for HPPD suggest that anxiety reduction, muscle relaxation, and re-framing one's visual phenomena through personal destigmatization and normalization may be helpful.

CBT has likewise shown promise for depersonalization-derealization disorder,[54] which occurs as a common comorbidity to HPPD and seems to share many of the same catastrophic thoughts.

[55] The Perception Restoration Foundation hosts a Specialists Directory that lists professionals with prior experience or relevant expertise in helping those with HPPD.

In the second episode of the first season of the 2014 series True Detective ("Seeing Things"), primary character Rustin Cohle (Matthew McConaughey) is depicted as having symptoms similar to HPPD such as light tracers as a result of "neurological damage" from substance use.

In addition, visual problems can be caused by brain infections or lesions, epilepsy, and a number of mental disorders (e.g., anxiety, delirium, dementia, schizophrenia, Parkinson's disease).