The same author reported two cases of cannabis-induced visual disturbances and correlated anxiety features. In both cases, Clonazepam (2 mg/day) was effective in improving symptoms, but focal visual disturbances without anxiety (trailing phenomena in one case, and black moving spots in the second case) persisted during and after therapy 19. More recently, Clonazepam (6 mg/day) has been proved to be effective in improving cannabis-induced HPPD symptoms 50. On the other hand, the intrinsic abuse potential of benzodiazepines might be inconvenient in certain individuals with a past history of substance use 17,18. Given the benign nature of HPPD I, the use of benzodiazepines should be proposed only for severe cases, in the acute phase, and for the short term.
Results
As a common practice, comparisons were made against normative population data to address this limitation. The unadjusted comparison of the HPPD group with the non-using control group pointed towards lower performance in the digit symbol drug addiction test. Originally considered a measure of complex attention, this test is now recognized for assessing a wide range of cognitive abilities, including attention, psychomotor speed, visual-perceptual functions, and executive functioning42. The results of the neuropsychological assessment of the HPPD group and the non-using control group are summarised in Table 4.
Hallucinogen-Related Disorders
- It is not uncommon for depersonalization-derealization to be the most distressing symptom of the condition.
- I would like to express my gratitude to all participants for their commitment andwillingness to travel long distances to participate in this study.
- Propensity scores were estimated through logistic regression, and parameters including low Standardised Pair Difference, eCDF statistics, and variance ratios close to one35 were used to assess balance quality.
Nonetheless, these analyses may still offer indicative insights to be further explored in future studies. The matching procedure was employed to compare the HPPD cases with hppd symptoms appropriate control groups and ensure covariate balance. To achieve optimal balance between the HPPD and control data, various matching strategies, such as Nearest Neighbour Matching, Optimal Pair Matching, and Optimal Full Matching, were evaluated based on recommendations from Greifer34. Propensity scores were estimated through logistic regression, and parameters including low Standardised Pair Difference, eCDF statistics, and variance ratios close to one35 were used to assess balance quality. The Optimal Pair Matching method demonstrated the most suitable parameters and was selected as the preferred approach for matching in this study.
Clinical visual characteristics of the HPPD group
Some types of therapy used to treat those conditions may be helpful in managing HPPD symptoms as well. To evaluate the individual performance of participants in the HPPD group, their test scores were transformed into z-scores or percentile ranks (PR) relative to reference samples detailed in the respective test manuals. Scores falling below a z-score of –1 or a PR of 16 were classified as below average. This approach is informed by the neuropsychological criteria for identifying possible deficits in mild cognitive impairment (MCI), as outlined by Jak et al.33. MCI was chosen as an orientation because it represents the mildest clinically relevant level of cognitive impairment.
Hallucinogen persisting perception disorder
- Hallucinogen-persisting perception disorder (HPPD) causes a person to keep reliving the visual element of an experience caused by hallucinogenic drugs.
- Regarding the pathophysiology of HPPD, current neurobiological hypotheses suggest disturbances in visual pathways as underlying etiopathology of the disorder15.
- The main group of symptoms reported are visual disturbances, which are more common than auditory disturbances.
According to DSM-5, Hallucinogen Persisting Perception Disorder is the recurrence of perceptive disturbances that firstly develop during intoxication. DSM-5 and previous DSM editions report a list of the most common symptoms experienced by HPPD patients, but only a few symptoms have been described in the professional literature. The main group of symptoms reported by Criterion A of the DSM-5 are visual disturbances. In fact, as in the vast majority of induced psychoses, visual hallucinations are notably more common than auditory 3. Regardless, every perceptual symptom that was experienced during intoxication may re-occur following hallucinogen withdrawal.
Visual oddities and disturbances with sudden paroxysmal onset have been interpreted as visual seizures and prompted the use of antiepileptic drugs in HPPD. This consideration helped to explicate the efficacy of benzodiazepines and led to the prescription of Phenytoin 75,76. Today, Phenytoin is not used for HPPD treatment due to its troubled side effect profile. In a single case of HPPD symptoms and electroencephalographic (EEG) abnormalities, compatible with toxic encephalopathy, the visual hallucinations that recurred at any alcohol ingestion improved, but did not disappear with the use of Valproic Acid (1500 mg/day) 46. Levetiracetam has shown to reduce some visual symptoms as well as HPPD related-depersonalization and derealization 80. Lamotrigine has shown to be efficacious in a recent severe case of HPPD with some EEG abnormalities (Anderson et al., 2018).
