Environmental treatments for problems of mood often use natural elements, such as light. In its simplest form, light therapy may involve going for a walk first thing in the morning every day. This allows sunlight to naturally reset your inner clock. Your inner clock, or circadian clock, cycles at about twenty-four hours, but the exact amount of time varies from person to person. Curiously, light that enters the eye activates both our visual system, and our circadian clock.

You can find out more about light therapy in this section. You can also access summaries of the research on, and clinical applications of, light therapy in our Treasury. Our short overviews for the general reader are followed by a list of key scholarly references.

Another environmental treatment boosts the balance of negative air ions in the circulation. Negative air ion level is commonly deficient in homes, schools, and work places—an unintended byproduct of the built environment. This man-made interference with optimum air quality—which can also be caused by adverse weather conditions—may underlie a wide range of physical and psychological problems, yet can be rectified using  negative air ionizers and humidification. Importantly, Nature provides its own means of ion replenishment, with the pounding surf at sea’s edge, by waterfalls and in tropical rain forests, and in the aftermath of lightning storms.