Key Findings

Psychological Impacts

  • LEDs can improve mood and cognition when used thoughtfully. Blue-heavy LED light (464–564nm) shows promise in treating Seasonal Affective Disorder (SAD), performing comparably to high-output fluorescent light boxes—despite using lower lux levels.

  • Higher color temperature LEDs (above 6000K) can enhance arousal, task performance, and perceived alertness in workplace settings. However, studies also suggest that perceived benefits may result from brightness alone, not just spectral content.

  • Excessive blue light exposure can disrupt melatonin and increase cortisol, impairing sleep and long-term emotional health. Balance is key: LEDs can support wellness when thoughtfully deployed, but overuse—especially at night—carries real risk.

Physiological Impacts

  • Blue light suppresses melatonin - the hormone responsible for regulating sleep - and may lead to chronic stress via increased cortisol production. This is especially relevant for those exposed to artificial light at night, such as night-shift workers or hospital staff.

  • Heart rate variability studies indicate elevated cardiac stress under blue-rich lighting compared to red-spectrum alternatives.

  • Preliminary animal studies (e.g., in rats) raise concerns about potential retinal damage from high-intensity blue light. While human data is limited, regulatory frameworks (like the EU's RG1 “Low Risk” classification) encourage caution in high-output applications.

  • Children under 8 are particularly sensitive to blue and UV light, suggesting pediatric-focused lighting strategies are overdue.

Indirect and Environmental Impacts

  • LEDs in agriculture show promise: blue and red LED mixes can enhance the nutritional value of plants like kale sprouts—boosting antioxidants, Vitamin C, and taste quality. This could translate to healthier food with lower environmental costs.

  • Light pollution is getting worse. Even though LEDs are energy-efficient, their blue wavelength content scatters more in the atmosphere, contributing disproportionately to skyglow. This affects everything from nocturnal wildlife to our own connection to the night sky.

  • Certain LEDs attract fewer insects than older CFLs, especially those with reduced blue/UV emissions. This has implications for both pest control and ecological preservation - but more research is needed.

Why It Matters

LEDs aren’t inherently good or bad, but our choices around how and where we use them matter. As designers, we have a responsibility to engage critically with the technologies we specify - not just for energy savings, but for their sensory and biological consequences. This literature review reminds me that every fixture matters.