---
title: "Safety of Stroboscopic Light Stimulation: Observational Evidence and Guidelines"
id: "plos-one-23-stroboscopic-light-stimulation-safety-within-and-beyond-laboratory-settings"
canonical_url: "https://medichelpline.com/clinical-feed/plos-one-23-stroboscopic-light-stimulation-safety-within-and-beyond-laboratory-settings"
content_type: "clinical_feed_article"
specialty: "Neurology"
source_name: "PLOS ONE (Medicine)"
source_url: "https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0359958"
published_at: "2026-10-14T14:00:00.000Z"
evidence_level: "Journal Feed"
license: "CC-BY-NC-4.0 / Informational Use"
---
# Safety of Stroboscopic Light Stimulation: Observational Evidence and Guidelines
## Provenance & Clinical Metadata
- **Canonical URL:** https://medichelpline.com/clinical-feed/plos-one-23-stroboscopic-light-stimulation-safety-within-and-beyond-laboratory-settings
- **Specialty:** [Neurology](https://medichelpline.com/clinical-feed/neurology.md)
- **Primary Source:** PLOS ONE (Medicine)
- **Source URL:** [Original Journal Publication](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0359958)
- **Published At:** 2026-10-14T14:00:00.000Z
- **Evidence Rating:** Journal Feed
## Executive GIST (TL;DR)
- **Stroboscopic Light Stimulation** (SLS) can trigger visual hallucinations and affects various users. - Study reviewed safety across four lab environments and included data from two commercial platforms. - 20 non-serious interruptions were reported, without serious adverse events or seizures. - Commercial data showed nine notable medical events from 3.8 million sessions. - Risk of visually provoked seizures noted, particularly for susceptible individuals. - Recommendations include the **Sussex Strobe Safety Screening Questionnaire** (4SQ) for risk management. - Tolerability issues, including discomfort, vary with anxiety, migraines, and sensory sensitivities.
## Clinical Analysis & Structured Key Points
Stroboscopic light stimulation safety within and beyond laboratory settings: Observational evidence and practical guidance | PLOS One Browse Subject Areas ? Click through the PLOS taxonomy to find articles in your field. For more information about PLOS Subject Areas, click here . Article Authors Metrics Comments Media Coverage Peer Review Reader Comments Figures Figures Abstract Stroboscopic light stimulation (SLS) reliably evokes geometric visual hallucinations and, in some contexts, altered-state experiences. Its increasing use in research, public, recreational and exploratory clinical settings creates a need for proportionate safety guidance. The main concern is a visually triggered seizure in a susceptible individual; reported non-epileptic responses include discomfort or distress. We combined a retrospective survey of safety practices and reported events across four laboratories, provider-reported operational data from two commercial SLS platforms, and a focused review of photosensitivity and sensory intolerance. Laboratory contributors reported 20 non-serious events that interrupted or modified participation, with no reported seizures or syncopal episodes. One commercial provider reported nine medically important or otherwise notable events across approximately 3.8 million sessions. The other reported five such events across more than 400,000 sessions. Because commercial adverse-event capture was passive and the laboratory protocols and monitoring procedures were heterogeneous, these figures cannot be used to estimate incidence or establish screening effectiveness. This synthesis informed a provisional Sussex Strobe Safety Screening Questionnaire (4SQ) and a layered, context-specific risk-management approach. The resulting framework distinguishes non-serious tolerability concerns from the principal medical risk of a visually provoked seizure in a susceptible individual, and supports conservative monitored familiarisation exposure, immediate stopping procedures and systematic adverse-event surveillance. The predictive performance of the 4SQ and the effectiveness of these precautions require formal evaluation; absolute SLS risk remains uncertain. Citation: Schwartzman DJ, Hewitt T, Schmidt TT, Sander JW, Nacker D, Thurbon J, et al. (2026) Stroboscopic light stimulation safety within and beyond laboratory settings: Observational evidence and practical guidance. PLoS One 21(10): e0359958. https://doi.org/10.1371/journal.pone.0359958 Editor: Gennady S. Cymbalyuk, Georgia State University, UNITED STATES OF AMERICA Received: April 21, 2026; Accepted: September 21, 2026; Published: October 14, 2026 Copyright: © 2026 Schwartzman et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: The aggregate reported-event data, survey instrument, 4SQ and accompanying coding documentation are available in the OSF repository at https://osf.io/nwkev/overview?view_only=c9979a478c734e7a9e46e50b5bed5c3a . The shared materials are aggregate and non-identifiable. The authors received no identifiable participant-level data. The underlying source records supplied by laboratories and commercial providers are not publicly shared where institutional, privacy or commercial restrictions apply. The repository documents the provenance of the shared aggregate records and the limits on their interpretation. Funding: D.J.S. is supported by a Medical Research Council grant (UKRI083). A.K.S. is supported by European Research Council Advanced Investigator Grant 101019254. T.H. is supported by the Margaret Boden PhD Scholarship from the University of Sussex. F.M. was supported by the AHRC/UKRI Project SENSOR grant (AH/Y007638/1). J.W.S. is based at the NIHR University College London Hospitals Biomedical Research Centre and receives research support from the Marvin Weil Epilepsy Research Fund, the Academy of Medical Sciences and the NIHR. F.M., T.H., D.J.S. and A.K.S. also received UK Government/UNBOXED 2022 funding, via Collective Act Ltd, to support their participation in the Dreamachine programme. The named public funders had no role in the analysis of this retrospective synthesis, the decision to publish, or preparation of the manuscript. UK Government/UNBOXED 2022 funding supported the Dreamachine programme from which part of the source data arose. Collective Act Ltd delivered the Dreamachine programme and collected source data that contributed to this synthesis; its role in data collection and the involvement of the named authors are reported in the author-contribution and competing-interests statements. The commercial SLS providers supplied aggregate operational information but provided no financial support, equipment, or other material support for this study. Competing interests: T.G. is affiliated with Lumenate Growth Ltd, G.L. is affiliated with Audyssey, and J.S. is affiliated with Roxiva Innovations Ltd. These affiliations are declared in the author list and are relevant to the commercial stroboscopic light stimulation contexts discussed in this article. All other authors declare no competing interests. This does not alter our adherence to PLOS ONE policies on sharing data and materials. 1.0 Introduction Stroboscopic light stimulation (SLS), usually delivered to closed eyes at frequencies between ~5–50 Hz, evokes stroboscopically induced visual hallucinations (SIVHs) comprising dynamic geometric patterns and colours. Occasionally, more complex visual hallucinations, such as faces, people or scenes, are reported, as are altered-state experiences [ 1 – 3 ]. Comparable phenomena occur with open-eye stimulation using diffusion goggles [ 4 ]. As SLS use expands beyond specialist research laboratories, clear and proportionate safety frameworks are required. Contemporary SLS research has addressed multiple, partly overlapping aims, including investigation of the neural correlates of SIVHs using fMRI and EEG, particularly in relation to neural entrainment and thalamocortical dynamics [ 1 , 5 – 13 ]. These studies often combine electrophysiological and phenomenological measures to relate neural dynamics to subjective visual experience. SLS has also been used to examine altered states of consciousness (ASCs; [ 2 , 11 , 14 , 15 ]) and to model simple visual hallucinations [ 7 , 16 , 17 ]. Interest has grown in the potential therapeutic applications of SLS, particularly at gamma (~40 Hz) and alpha (9–11 Hz) frequencies, for conditions such as Alzheimer’s disease and depression [ 18 – 21 ]. However, the evidence for therapeutic benefit remains preliminary and inconclusive [ 18 , 22 ]. Against this backdrop, we synthesise cross-laboratory safety practice, retrospective reported-event data and operational reports from two commercial SLS providers, alongside a focused review of photosensitivity and sensory intolerance. Our aims are to describe current practice, identify recurrent tolerability and safety considerations, and develop a provisional, evidence-informed screening checklist for formal evaluation. The available data characterise reported adverse responses and recurrent safety considerations but cannot establish population incidence or screening effectiveness. 1.1 Medical risks and sensitivities associated with SLS Primary risk factor: Photosensitive seizure. The main medical concern associated with SLS is a visually provoked seizure in an individual with photosensitivity. Photosensitive epilepsy (PSE) refers to epilepsy in which seizures can be provoked by visual stimuli. A photoparoxysmal response (PPR) is an epileptiform electroencephalographic response to visual stimulation; it indicates photosensitivity but is not itself a clinical seizure or an epilepsy diagnosis [ 23 , 24 ]. Photosensitivity is more common in younger people [ 23 ] and in particular epilepsy syndromes [ 24 ], but can occasionally persist or present later in life [ 23 , 25 ]. Photophobia instead refers to discomfort or intolerance associated with light and should not be treated as synonymous with PSE [ 26 ]. These distinctions are important because the present synthesis includes medical events and non-serious tolerability outcomes. Factors mainly relevant to visually provoked seizures or seizure susceptibility include a personal history of epilepsy or seizures, a first-degree family history of photosensitive epilepsy, or younger age. Photosensitive seizures are heritable [ 24 ], and genetic susceptibility contributes broadly to epilepsy [ 27 ]. Other factors may include sleep deprivation, recent alcohol or recreational drug exposure, acute illness, and some medication or withdrawal contexts. These factors do not contribute equally and should not be combined into a single risk score. PSE is significantly more common in children and adolescents than in adults [ 23 ], although later-life photosensitivity has also been documented [ 25 ]. Sleep deprivation can increase seizure likelihood in people with epilepsy [ 28 , 29 ]. Reduced sleep can increase cortical excitability and epileptiform discharges, particularly in idiopathic generalised epilepsies [ 28 – 31 ], while diary-based and longitudinal studies have reported increased seizure risk after acute sleep loss [ 32 , 33 ]. Medication-related risk is instead drug-, dose- and context-specific and may be concentrated during toxicity, recent dose change, withdrawal, interacting illness or combinations of pro-convulsant factors. Pregnancy involves physiological, hormonal and psychological changes that may influence seizure control across trimesters [ 34 ]. Altered drug metabolism, disrupted sleep, stress and fatigue may further affect seizure susceptibility during pregnancy. Because direct evidence on SLS during pregnancy is lacking, pregnancy should be treated as a precautionary exclusion in research protocols rather than as an established SLS-specific risk factor. Secondary risk factors: Sensory sensitivities and photophobia. Separate from seizure susceptibility, anxiety, migraine or photophobia, sensory sensitivity, and active psychiatric symptoms may affect the tolerability of SLS. Evidence linking these characteristics to serious SLS-related medical events is limited; they are mainly potential markers of discomfort, distress or early withdrawal rather than established seizure predictors. Below, we summarise these sensitivities along with their prevalence. Anxiety. In the UK, medical consultations for anxiety have recently increased markedly [ 35 ]. Across adult populations, prevalence estimates range from 3.8% to 25% of the population [ 36 ]. Anxiety and panic disorders have been associated with reduced tolerance to light [ 26 ], while flicker can evoke visual discomfort [ 37 ]. These observations support treating anxiety as a potential tolerability factor; they do not establish anxiety as a predictor of serious SLS events. Migraine. Migraine affects approximately 14–15% of people globally and accounts for about 4.9% of years lived with disability [ 38 ]. Photophobia is common; bright or flickering light is frequently reported as a trigger, although apparent triggering may sometimes reflect photophobia during the premonitory phase [ 26 , 39 ]. High-contrast SLS may therefore be less tolerable for some people with migraine. ASD. NICE estimates that autism affects around 1.1% of UK adults [ 40 ]. Sensory hypersensitivity and heightened physiological responses to sensory stressors have been described in studies of autistic children [ 41 , 42 ], although these features are heterogeneous and not universal. In this adult framework, the relevant screening target is self-reported visual or sensory intolerance, not the diagnosis itself. ADHD. In an online survey, photophobia was self-reported by 69% of adults with ADHD or ADHD symptoms and 28% of respondents without ADHD [ 43 ]. ADHD itself is not a contraindication; the relevant consideration is self-reported light discomfort or sensory intolerance. Psychosis. Global estimates place the prevalence of schizophrenia at around 0.3%, although estimates vary by method [ 44 , 45 ]. Because SLS evokes vivid visual phenomena, active psychotic symptoms may plausibly increase distress or confusion; this is a precautionary inference rather than evidence of an SLS-specific event rate. 1.2 Public incidents shaping perceived risk and regulation Several widely reported incidents have shaped risk perception and regulation of flashing visual stimuli. The 1997 “Pokémon incident” in Japan involved rapidly alternating red-blue flashes at approximately 12 Hz, followed by seizures and other symptoms in many viewers, including some children without a previous epilepsy diagnosis [ 46 ]. Japan subsequently introduced broadcasting restrictions on provocative flashes and saturated-red flicker [ 46 ]. The London 2012 Olympics’ promotional footage was withdrawn following public reports of seizures associated with the animation, although these reports did not medically verify these events [ 47 ]. These broadcast and public-event examples establish the importance of provocative stimulus characteristics, but are not directly comparable with screened, closed-eye laboratory SLS. 1.3 Current screening practice Screening protocols vary widely in context, scope, design, and their evidence base. Laboratory studies typically use bespoke self-report questionnaires to exclude known PSE and other neurological or psychiatric vulnerabilities. In contrast, public installations often rely on simplified health declarations or verbal briefings with varying degrees of formality. Both approaches have limitations, as many focus narrowly on epilepsy, overlooking other clinically relevant sensitivities. Protocols are also context-specific and often insufficiently documented for replication or cross-study comparison. To address these gaps, we developed the Sussex Strobe Safety Screening Questionnaire (4SQ) as a provisional, evidence-informed, non-diagnostic checklist designed to support structured risk review and proportionate precautions. It integrates neurological, psychiatric, sensory, medical, substance, sleep and medication considerations, but its predictive performance and effect on adverse events will require formal evaluation. 2.0 Methods Ethics, consent and data governance This study was a secondary analysis of anonymised, non-identifiable summary information supplied by contributing laboratories and commercial providers. We did not recruit participants for this synthesis and did not receive or access identifiable participant-level data. Under University of Sussex institutional guidance, analysis of these non-identifiable secondary data did not require new research ethics review or a separate participant-consent process. Participants in the contributing academic studies provided informed consent before taking part under the relevant local ethics procedures; depending on the study format, consent was recorded in writing or electronically. Commercial providers supplied aggregate, non-identifiable operational reports rather than participant-level research data. Their users were not recruited as research participants in this synthesis, and the providers did not seek research consent from them for this secondary analysis. Any service-use safety acknowledgements obtained by the providers were not treated as research consent. 2.1 Cross‑laboratory and commercial data acquisition on SLS safety and practice On 24 July 2025, a structured Qualtrics portal was distributed to four SLS research groups and two commercial providers with substantial SLS experience; the data were accessed 28 days later, on 21 August 2025. It requested the contributor’s identity and reporting scope; reporting period; number and purpose of studies or sessions; device, eye state, frequency, brightness and duty cycle; participant or user counts; screening and risk-management procedures; and event narratives or supporting documents. A major event was defined as a seizure or another negative outcome with medical implications, and a non-serious event as a negative outcome that obstructed or stopped participation without reported medical implications. Contributors retrospectively determined which events met these definitions. Event descriptions were supplied by the contributing teams and were not independently confirmed against medical records. For online studies, follow-up was limited to information available to the original research teams. Narratives were grouped post hoc into descriptive symptom categories, using the primary stated reason for stopping when several symptoms were reported. Because populations, protocols, exposure units and surveillance procedures differed, we report sources separately and do not treat the synthesis as a meta-analysis. Research laboratories. Four research laboratories contributed data from studies conducted between 2020 and 2025 in the UK, Germany, the Netherlands and Australia. The studies involved mainly healthy participants, alongside adults reporting depressive symptoms. Contributor summaries described one study from Lab A (reported N = 20), twelve from Lab B (N = 461), six from Lab C (N = 480) and five from Lab D (N = 109). These are reported study totals rather than verified unique-person denominators: some study-level sample sizes were unavailable, and participation in more than one study could not be excluded. Where available, laboratories provided summary information on screening procedures and adverse-event logging. SLS characteristics. Across laboratories, SLS was delivered using commercial and custom hardware. Devices included commercial stroboscopes (Lucia N003, Light Attendance GmbH, Innsbruck, Austria; Roxiva RX1, roXiva Ltd); custom-built stroboscopes (Lumenate Growth Ltd, Bristol, UK; University of Sussex); a projector (Epson EB-G7400U); and standard computer monitors at maximum brightness. Commercial SLS providers. Data from two commercial SLS providers were obtained. Provider A operates a mobile application delivering closed-eye SLS through a smartphone flashlight, with frequency, brightness and duty cycle modulated in synchrony with audio. It reported approximately 3.8 million sessions from 2021 to 2025 and approximately one million users. As reported sessions substantially outnumber users, repeated use contributes to the session total. The dataset does not establish whether reported events were followed up independently or whether adverse-event capture was complete. Provider B manufactures a configurable LED SLS device used in individual and group settings with more than 400,000 sessions over approximately five years. This is a minimum reported operational session count rather than a unique-user denominator: the same user could contribute more than one session, and additional consumer use was not included. Event reporting was passive and the completeness of follow-up is unknown. The two providers are described separately. 3.0 Results: Laboratory-based studies 3.1 Laboratory-based SLS survey Most studies (n = 21) used fixed-frequency SLS with reported frequencies spanning 1–80 Hz; all used a square-wave SLS signal. Stimulation protocols typically used frequencies within the alpha frequency range (8–12 Hz; n = 9), with one laboratory also testing 15 Hz stimulation. A subset (n = 3; total n = 95) used dynamic frequency shifts between 3 and 15 Hz. Flash duration and inter-flash interval varied, with most protocols adopting a 50% duty cycle (equal flash and inter-flash interval), with values ranging from 25% to 75%. Brightness levels varied by device: mean luminous flux for stroboscope-based setups was ~ 5,373 lumens (SD = 326); the projector operated at 447.2 cd/m 2 ; monitor setups typically delivered ~300 cd/m 2 . As luminous flux (lumens) and luminance (cd/m 2 ) quantify different properties, these values are not dir
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