For countless millennia, humankind had a single primary source of light: the sun. It governs our circadian rhythm – we are active when it’s light and rest when it’s dark.
There are three receptors in our retinas: cones and rods, and the “third receptor” discovered in 2002. The third receptor communicates directly with the part of the brain which controls our circadian rhythm and our biological clock. Thanks to this discovery, we finally established a connection between human well-being and access to light. This receptor affects the secretion of the sleep hormone melatonin and the stress hormone cortisol.
A lack of light affects us negatively
Melatonin production increases when light levels are lower and in the dark (night time), while cortisol production increases when light levels are high (day time). Too little light can make us feel down, especially during the winter months (SAD – Seasonal Affective Disorder). Light therapy has long been used in healthcare to reduce the effects of seasonal affective disorder.
Today, around 60% of the Swedish workforce works indoors in some type of office environment under artificial light for at least 25% of the working day. Healthcare staff and school personnel also spend most of their working hours indoors. When planning lighting, it’s important to take into consideration the need for adapted light for staff, students, patients and customers.