Effects of evening indoor light exposure on sleep and circadian functioning in autistic people: A scoping review

Sleep difficulties are highly prevalent among people with autism spectrum disorder (ASD), substantially affecting their well-being and daily functioning. Although the role of indoor light exposure, particularly during evening hours, is well-established in melatonin regulation, circadian functioning, and other physiological responses in general population, its non-visual effects in autistic people remain underexplored. Therefore, we aimed to provide an overview of existing evidence addressing indoor evening light exposure and its effects on sleep, circadian, and other related physiological functioning in autistic people. The search was carried out in PubMed, Scopus, ScienceDirect, Web of Science and PsycINFO databases, and eight studies were identified after applying the eligibility criteria. Our analysis demonstrated significant methodological limitations, including reliance on traditional lighting metrics, absence of thoroughly controlled interventions, and limited attention to heterogeneity in ASD profiles. While none of the studies explicitly aimed at the raised research questions, they still provided partial insights that could inform future research directions on the development of tailored lighting interventions, adoption of circadian-specific metrics, and inclusion of diverse ASD profiles to account for sensory differences. Findings also revealed the necessity for collaboration among fields such as lighting engineering, sleep medicine, and chronobiology to utilize the most appropriate light metrics and improve methodologies. Overall, this review highlights the need for evidence-based guidelines to enhance sleep, circadian alignment, and overall well-being for autistic people.