Introduction Hallucinogen perception persisting disorder (HPPD) can be defined as the re-experience of altered visual perceptions after use of psychedelic drugs [1,2]. Despite estimated high percentages of recreational use of psychedelic drugs, research data on HPPD are scarcely available [1,2]. Considering the recent emergence of studies on psychedelic drugs as a treatment option for various psychiatric disorders, proper assessment of potentially harmful side effects, such as HPPD, is necessary [3]. This study aims to investigate the association between lifetime use of HPPD-associated drugs and the presence and burden of visual hallucinations in a large general population sample.

Methods We used data from a large online survey on hallucinations in the general Dutch population, https://zieikspoken.nl, collected between September 26th, 2016 and May 23rd, 2017. All participants (n=10.289) were aged 14 or over. We assessed lifetime use of 11 commonly used recreational drugs in the Netherlands, out of which LSD, psilocybin, 2-CB and MDMA were considered HPPD-associated based on previous reports [1-4]. Visual hallucinations were assessed using the Questionnaire for Psychotic Experiences (QPE). Presence of visual hallucinations was categorized as follows: never experienced, ever experienced, experienced in past month, experienced in past week. Associations between lifetime use of HPPD-associated drugs and presence and phenomenology of visual hallucinations were calculated using Pearson’s chi-square tests in SPSS.

Results A total of 2.175 subjects (21.1% of all participants) indicated having used HPPD-associated drugs at least once in their lifetime. In subjects who had never experienced visual hallucinations, the percentage of lifetime HPPD-associated drug use (18.8%) was significantly lower than in the groups who had experienced visual hallucinations in their lifetime but not recently (23.0%), in the past month (25.2%) or the past week (24.9%). Nevertheless, lifetime use of HPPD-associated drugs did not differ between the groups of subjects with visual hallucinations (ever/past month/past week). Within the group of subjects with visual hallucinations in the past week or month, lifetime HPPD-associated drug users did not differ from non-users in terms of experiencing a significant burden from their visual hallucinations (25.2% vs. 24.1%, respectively; OR 0.9 (95%-CI 0.7-1.2)) or having visual hallucinations with a significant impact on their daily functioning (25.1% vs 23.0%; OR 0.9 (95%CI 0.6 -1.4)).