Delta sleep-inducing peptide was identified in the 1970s by Schoenenberger and Monnier, who found it in the blood of rabbits during induced slow-wave sleep and named it for what they believed it did. That name has done a great deal of work in the decades since. The subsequent evidence never really supported it: human studies were small, dated and inconsistent, and no modern randomised controlled trial demonstrates a reliable effect on sleep. It was reviewed by an FDA advisory committee in July 2026 under the name emideltide and was the only peptide of seven considered to be turned down. For insomnia, cognitive behavioural therapy remains the first-line treatment with far stronger evidence.