J Korean Neuropsychiatr Assoc.  2021 Aug;60(3):204-212. 10.4306/jknpa.2021.60.3.204.

A Study on the Relationship Between Mental Health Variables and Physical Activity Variables in the Clinical Group of North Korean Defectors: A Pilot Study

  • 1Department of Psychiatry, National Medical Center, Seoul, Korea
  • 2Department of Computer Science, Korea University College of Information, Seoul, Korea
  • 3Chronobiology Institute, Korea University, Seoul, Korea
  • 4Department of Psychiatry, Korea University College of Medicine, Seoul, Korea


This study is designed to extract a representative variable that distinguishes psychiatric patients of North Korean Defectors and a control group by using machine learning based on measured mental health variables and physical activity variables.
The physical and mental activity variables of 17 North Korean defectors that previously were hospitalized or received psychiatric outpatient treatment and a control group were compared. The survey focused on mental health variables that included contents related to depression, suicidal risks, post-traumatic stress disorder, anxiety, insomnia, physical symptoms, quality of life, coping skills, social support, and drinking. Physical activity variables included the number of steps walked per day, sleep time, and sleep efficiency were measured by Fitbit.
The 7th question of the Patient Health Questionnaire-9, “Trouble concentrating on things, such as reading the newspaper or watching television over the past two weeks,” showed the highest gain ratio by 84 percent. Based on the result of the decision tree, this single index may distinguish between the clinical and control groups.
A clinician may conduct a more effective interview with a North Korean defector by identifying in the early stages whether the patient has been having difficulty concentrating on daily tasks during the past two weeks.


North Korean defectors; Mental health variable; Physical activity variable; Machine learning; Gain ratio; Decision tree; Refugee mental health
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