Blue Spectrum Exposure and Neuropsychological Regulation: Implications for Therapeutic and Environmental Design

Exposure to water-rich and blue-toned environments-whether encountered in natural settings, daylight, or intentionally designed architectural spaces-has drawn increasing attention across environmental psychology, chronobiology, and healthcare design. Two largely separate bodies of evidence inform this paper: a well-established photobiological literature on how short-wavelength ("blue") light regulates circadian timing through melanopsin-containing retinal ganglion cells, and a growing but more heterogeneous literature on the psychological benefits of "blue space"-outdoor environments featuring visible water. This paper synthesizes both literatures using a structured narrative-review approach, evaluates the strength and limitations of the evidence in each domain, and proposes an integrative framework for therapeutic and environmental design. I argue that the two bodies of evidence should not be conflated: the circadian effects of blue wavelengths are mechanistically well-characterized, while the psychological effects of blue space are observational, much less mechanistically understood, and confounded with general nature exposure. I conclude with a revised set of design implications and a research agenda that reflects this distinction.