What is “darkness deficiency,” and why is it important to the integrative practitioner? In this interview, sleep expert Catherine Darley, ND, discusses the clinical relevance of darkness deficiency and how it can lead to a melatonin imbalance. She then describes newer clinical uses of melatonin beyond sleep and talks in depth about melatonin efficacy, dosage, and safety. Darley is the founder of The Institute of Naturopathic Sleep Medicine and an internationally recognized expert on sleep disorders.   About the Expert Catherine Darley, ND, is the leader in natural sleep medicine. She combines her knowledge of sleep disorders with her training as a naturopathic physician to bridge these 2 fields. As a naturopath, her expertise lies in providing natural and effective treatments for sleep problems. She treats people of all ages and especially enjoys working with teens and their families. She founded The Institute of Naturopathic Sleep Medicine Inc in Seattle, which is dedicated to patient care, public education about sleep health, and consultation with high-risk populations such as first responders. Darley regularly writes articles and trains healthcare providers in the treatment of sleep disorders. She has served as adjunct faculty at Bastyr University and the National University of Natural Medicine.