The secret of sleepless nights, which our ancestors described as the wandering of the spirit, can be explained in modern medicine as an intricate dance of neurotransmitters and hormones. At night, our brain releases a sleep hormone called melatonin to signal to the body that it is time to sleep. Melatonin is produced from serotonin, so when serotonin is deficient or not synthesized properly, issues arise with melatonin secretion as well.
In addition, there is a neurotransmitter in the brain called GABA. This substance works to calm brain activity and soothe arousal, but when stress is high or caffeine intake is excessive, the action of GABA is suppressed, keeping the brain awake. The Donguibogam's description of an anxious spirit intuitively captures this very state of complex chemical imbalance in the brain.
In particular, chronic stress is the greatest enemy of sleep for people today. When stress persists, our body continues to secrete cortisol, which overactivates the sympathetic nerve day and night. When the sympathetic nerve is activated, heart rate quickens, blood pressure rises, and the body remains tense, making it difficult to fall asleep comfortably no matter how tired you feel. It is as if the body wants to rest, but the brain keeps warning that it is dangerous and you must stay awake.
Inside our body, an area called the suprachiasmatic nucleus regulates the biological clock. This clock is guided primarily by light and regular daily routines. When you are exposed to blue light from smartphones or computers late at night or keep an irregular schedule, the biological clock gets disrupted, melatonin secretion is suppressed, and sleep quality drops sharply. Beyond simply missing sleep, poor sleep quality can lead to weakened immunity, chronic inflammation, cognitive decline, mood disorder, and even metabolic disease such as insulin resistance or obesity. Sleep is the most essential time when every system in the body and mind resets.
