A warm welcome-back to Abigail Strubel, social worker, writer, mental health advocate, and chronotherapy aficionado. Here she delves into some surprising historical precursors of light therapy for both medical and psychological afflictions, which demonstrated positive effect long before the current era of definitive placebo-controlled clinical trials.

Pioneering nurse Florence Nightingale was rigorous not only about kindness and cleanliness — she maintained meticulous statistical records about her patients to determine the most effective treatment practices.

In addition to encouraging good ventilation, promoting adequate sleep, providing a nutritious diet, and allowing plants and flowers in the sickroom (she knew that they provide oxygen and consume carbon dioxide, as well as provide a pleasant focus), Nightingale was an enthusiastic proponent of allowing as much natural light into the patient’s room as possible.

As she wrote in Notes on Nursing, “It is the unqualified result of all my experience with the sick, that second only to their need of fresh air is their need of light…And that it is not only light but direct sun-light they want.” She knew that her patients in rooms facing east recovered more quickly than those in rooms facing other directions — or in windowless rooms. She observed her patients turning their faces toward light and compared them to plants following the sun in its course across the sky. We cannot be sure whether this light acted as a mood and energy enhancer in the hospital room or also contributed to ridding of her patients’ infections or other disease processes. But her realization was perspicacious and foretold of light therapies, in various forms, that continue in active development.

Similarly, before the development of antibiotic therapy for tuberculosis, sanatoriums addressed the worldwide pandemic with sunlight. Doctors noted that patients who lay in the morning sun gained more weight and went home sooner. This became standard practice around the world:

• In 1903 Swiss doctor Auguste Rollier opened his “sunlight clinic,” which featured an enormous solarium on the roof and developed a slow, careful tanning process for new or especially feeble patients. Here, the ultraviolet (UV) component in sunlight, acting on the skin—now understood as carcinogenic in high doses — was the presumed mode of action, although the patients may also have benefitted from the mood and energy boosts of light to the eyes.
• Deep in a Finnish forest, in 1929 architect Alvar Aalto built a sanatorium that prioritized access to natural light, enabling patients to benefit from the sun while resting comfortably in their rooms. Light through the windows would have substantially reduced UV exposure, and the benefit of such filtered light to the eyes seems likely to have involved the mood-energy effect.
• In the early years of the 20th century, my great-grandparents ran a tuberculosis sanatorium in the beautiful town of Otwock, Poland. The air was clear, the climate was sunny, and the patients — when they weren’t eating one of their eight daily meals — spent their time lying quietly in the sun, well bundled up in autumn and winter. Bundling up outdoors in fall and winter, when UV levels from skylight are lower than in spring and summer, again imputing mood-energy enhancement mediated by visible light.

What Nightingale observed more than a century ago, modern science has now proven. Sunlight reaching the eyes can reset a person’s circadian rhythms, enabling a healthier sleep-wake cycle and better healing. And it can be deployed strategically to treat mood disorders in particular. Don’t take my word for it — here’s some more recent evidence:

• Pioneering chronotherapist Francesco Benedetti and his colleagues found that patients suffering from bipolar depression who were placed in rooms with an eastern exposure with earlier morning sunlight recovered almost four days faster than patients whose rooms had a western exposure. Similarly, another study found that patients admitted to two hospitals for depression — one with sunny rooms, one with darker rooms — stayed approximately three days less if they were in the sunnier rooms.
• Benedetti also demonstrated that artificial sunshine from light therapy lamps can be an effective, non-invasive, and safe intervention for bipolar depression, which can be difficult to treat with antidepressants, and their hit-or-miss effectiveness for individual patients. The risk of triggering a manic or mixed episode of the disorder was very low, certainly no higher than with the drug therapies.
• A 2013 study of patients with cystic fibrosis and co-morbid depression suggested that exposure to light significantly improved patients’ chance of depression remission.
• A review of hospital admissions in Egypt, a country with year-round sunshine and a fairly stable climate, showed more admissions for depression in December, and more admissions for mania in June. In contrast, schizophrenia admissions did not vary by season. This is consistent with a large body of research that suggests that bipolar disorder is a circadian rhythm disorder.

A modern heir to Rollier and Aalto is Dr. Richard Hobday, who is what the British call a “chartered engineer.” I might not recognize that term, but I’m impressed by his research and practice. Hobday’s book, The Light Revolution: Health, Architecture and the Sun, delves into the history of how sunlight has been used to alleviate conditions ranging from rickets to heart disease. He advocates “5 Points of Solar Architecture for Health”:

1. Orient the building for sanitation and sunbathing.
2. Position the rooms for sunlight therapy and disinfection.
3. Put windows in more than one wall to let the sun in at different times of the day or year.
4. Ventilate naturally.
5. Underfloor heating.

As I prepare for a surgery in the spring (once the winter burden of SAD has passed), I’m definitely going to ask the hospital if I can be placed in a room with an eastern exposure. And after I go home, I’ll be sure to spend plenty of my recovery time relaxing (well-sunscreened) in Central Park, soaking up the healing sunlight.