Have you ever wondered why you cannot sleep even when your body is completely exhausted? Modern medicine explains this stress-induced insomnia through complex interactions between the brain and hormones. What Donguibogam described as a deficiency of heart blood or the spirit being unable to rest peacefully can be understood in modern terms as brain hyperactivation and hormonal imbalance.
When we experience stress, an emergency system called the hypothalamic-pituitary-adrenal axis is activated in the brain. This system secretes large amounts of stress hormones like cortisol, putting our body into a fight-or-flight response state. Normally, cortisol peaks in the morning and drops toward the evening to allow sleep, but chronic stress keeps this cortisol secretion high even at night. It is as if an alarm bell continues ringing at night, keeping the brain in a continuous state of tension.
Furthermore, stress disrupts the balance of neurotransmitters in the brain. The function of gamma-aminobutyric acid, which relieves tension and induces sleep, declines, while substances that induce brain arousal, such as norepinephrine and dopamine, may be secreted excessively. What Donguibogam described as deficient heart blood preventing the spirit from resting peacefully can also be interpreted as a state where impaired blood circulation fails to supply adequate nutrients and oxygen to the brain, disrupting neurotransmitter balance and preventing the brain from settling down.
In particular, ruminative thinking—where events of the day or future tasks race through your mind before falling asleep—excessively activates the frontal lobe of the brain. This state prevents the brain from halting its commands and switching into rest mode, much like an engine running without pause. The autonomic nervous system of our body is also affected. Stress stimulates the sympathetic nerve, raising heart rate and blood pressure while tensing muscles, thereby maintaining the entire body in an aroused state. Sleep comes comfortably only when the parasympathetic nerve takes dominance, but stress leaves no room for that.
These combined actions also adversely affect the secretion of melatonin, the hormone that determines sleep quality. Melatonin is secreted in darkness to signal to our body that it is time to sleep, but when cortisol is too high or the sympathetic nerve is hyperactivated, melatonin secretion can be suppressed. Ultimately, stress disrupts our biological clock and interferes with the natural process of falling into deep sleep, becoming the main culprit behind tossing and turning all night. You are not staying awake simply because you have a lot on your mind; complex physiological and neurological changes are taking place inside your body.
