Advanced Sleep Phase Syndrome - Suite101.com Scientists have found that exposing the subject to artificial light strong enough to resemble daylight can alter circadian rhythms. The reason that light therapy works as well as it does is that light affects the pineal gland. The pineal gland secretes melatonin which helps us sleep. When light is taken away, the secretion of melatonin increases and we begin to get drowsy. It is thought that in people who have ASPS, the connection between light, the pineal gland, and melatonin secretion is so strong that almost immediately as the sun goes down, melatonin production starts up and the poor ASPS sufferer immediately begins to think that it