Abstract: The present disclosure generally relates, in certain embodiments, to light-based treatments. In some case, a subject having or at risk for a condition such as insomnia can be treated, e.g., with light, such as green light. Other conditions include sleep disorders such as sleep apnea and other indications. In some cases, the light that is administered to the subject may be green light, or the light may have a characteristic wavelength only in a wavelength range between 510 nm and 550 nm with a bandwidth no larger than 20 nm full-width-half-maximum. Other embodiments described herein are generally directed to systems for treating such conditions, kits for treating such conditions, or the like.