[Reading Science] The Real Scientific Reasons Why 'Hakpok' Is Truly Harmful

South Korean society is once again in turmoil over the issue of 'school violence (hakpok)'. Jung Soon-shin, the newly appointed head of the National Investigation Headquarters, ultimately resigned due to a school violence issue involving his son during high school shortly after his appointment. Although he was highly capable as a father and legal expert, he faced severe criticism for being lacking as a 'human being.' Moreover, numerous celebrities and athletes have been forced into retirement after being embroiled in school violence controversies following their rise to fame. This reflects how sensitive public opinion in South Korea is regarding school violence. Several dramas centered on school violence have gained popularity on global OTT platforms, making Korean school violence notoriously known worldwide.

Why is school violence bad? In fact, many people, especially those in their 40s and 50s and older generations, remain insensitive to the issue. Common reactions include, "Kids grow up by fighting," or "Why should adults interfere in kids' fights?" During harsh times such as the Japanese colonial era and the Korean War, and the remnants of military dictatorship, violence was normalized and chronic throughout society. Even until the 2000s, corporal punishment by teachers in schools was called the 'rod of love.' Although teacher authority is now often violated, back then, teachers could slap students dozens of times or beat them with sticks and kicks without any problem. Such violence left deep scars in the hearts of Koreans, manifesting in high suicide rates, intergenerational domestic violence, and widespread mental illnesses. This means that older generations should not respond insensitively based solely on their own experiences.

Recent research by Korean scientists reveals why school violence is harmful and why it must be thoroughly prevented. Through animal studies, they have specifically demonstrated how stress experienced in childhood before adulthood?such as parental abuse, bullying, and school violence?negatively affects the human brain. It was already known that early-life stress leads to personality disorders such as paranoia, depression, drug addiction, and antisocial behavior later in life. However, previous research focused mainly on genetic changes, and this is the first study to investigate actual changes occurring in the brains of victims.

Dr. Oh Se-jong and Dr. Choi Jae-yong, among others from the Korea Institute of Radiological & Medical Sciences, examined neurotransmitter conditions by injecting radiopharmaceuticals into mice subjected to stress. Six mice were separated from their mothers for 4 hours daily over 12 days starting from postnatal day 2 to induce maternal separation stress. Another six mice were confined in cylindrical plastic cages for the same period and duration to induce complex stress. The researchers then analyzed levels of neurotransmitters such as glutamate, GABA, and serotonin in the mice's brains. Positron Emission Tomography (PET), which uses radioactive substances to detect physiological and biochemical changes in living organisms, was employed.

The results showed that stressed mice had severe damage to neurotransmitters compared to normal mice. Mice subjected to maternal separation stress from postnatal day 2 showed reduced uptake of the inhibitory neurotransmitter GABA, which regulates excitation, by 19?27% in females and 7?12% in males compared to normal mice. The excitatory neurotransmitter glutamate, important for learning and memory formation, was reduced by 11?16% in females and 7?15% in males, while serotonin, which regulates emotions, was reduced by 19?28% in females and 7?11% in males.

□ After injecting radiopharmaceuticals that selectively bind to glutamate, GABA, and serotonin systems into the normal group, maternal separation group, and complex stress group, positron emission tomography (PET) was performed. Both the maternal separation group and the complex stress group showed lower neural PET uptake patterns of GABA, glutamate, and serotonin compared to normal rats, and these patterns were proportional to the intensity of stress.
□ In females, compared to males, there was no difference in the excitatory neurotransmitter GABA, but relatively lower brain uptake was observed in the inhibitory neurotransmitter glutamate system and serotonin related to mood.

* Areas where the radiopharmaceutical was absorbed are shown in red.

Notably, the greater the stress intensity, the more severe the damage. In cases where mice experienced both maternal separation and restraint stress?being separated from their mothers and then restrained in acrylic cages for 4 hours daily over 6 days at postnatal day 20?the uptake rates of GABA were 31?38% lower in females and 31?37% lower in males compared to normal mice. Glutamate uptake was reduced by 24?29% in females and 13?22% in males, and serotonin uptake was reduced by 27?35% in females and 11?19% in males. Additionally, females showed greater damage to glutamate and serotonin, which are crucial for learning, memory formation, and emotional regulation, indicating they are relatively more vulnerable to stress.

In the nervous system, excitatory and inhibitory neurons form various circuits and maintain a balance in circuit activity, which induces normal cognitive, thinking, and behavioral functions. Problems in regulating the balance of excitatory and inhibitory neural activity lead to various neurological disorders. However, understanding of the functional differences in excitatory and inhibitory neural activity mechanisms caused by early-life stress has been insufficient until now.

The research team explained, "In female mice exposed to stress during infancy and childhood, severe damage to glutamate and serotonin neurotransmitters was observed," adding, "This study not only provides a foundation for identifying causes of adult mental illnesses that may arise from childhood trauma but also offers evidence that could support the development of targeted treatments."