Blood biomarkers of Hikikomori, a severe social withdrawal syndrome

Abstract

Hikikomori, a severe form of social withdrawal syndrome, is a growing social issue in Japan and internationally. The pathophysiology of hikikomori has not yet been elucidated and an effective treatment remains to be established. Recently, we revealed that avoidant personality disorder is the most common comorbidity of hikikomori. Thus, we have postulated that avoidant personality is the personality underpinning hikikomori. First, we herein show relationships between avoidant personality traits, blood biomarkers, hikikomori-related psychological features, and behavioural characteristics assessed by a trust game in non-hikikomori volunteers. Avoidant personality traits were negatively associated with high-density lipoprotein cholesterol (HDL-C) and uric acid (UA) in men, and positively associated with fibrin degeneration products (FDP) and high sensitivity C-reactive protein (hsCRP) in women. Next, we recruited actual individuals with hikikomori, and compared avoidant personality traits, blood biomarkers, and psychological features between individuals with hikikomori and age-matched healthy controls. Individuals with hikikomori had higher avoidant personality scores in both sexes, and showed lower serum UA levels in men and lower HDL-C levels in women compared with healthy controls. This is the first report showing possible blood biomarkers for hikikomori, and opens the door to clarify the underlying biological pathophysiology of hikikomori.

Development and validation of the 25‐item Hikikomori Questionnaire (HQ‐25)

“…Data were collected between February 2014 and December 2016. Participants completed: (i) a semi‐structured diagnostic interview for hikikomori ; (ii) the item pool for the hikikomori scale; (iii) a self‐report survey, including sociodemographic items and measures of psychiatric symptoms and psychological constructs; and (iv) a computer‐administered test and blood sample, both used for a separate research study . The hikikomori scale item pool was re‐administered to a subsample of participants for evaluation of test–retest reliability.…”

Hikikomori : Multidimensional understanding, assessment, and future international perspectives

“…We have recently reported that individuals with hikikomori have higher avoidant personality scores in both sexes, and show lower serum uric acid (UA) levels in men and lower high-density lipoprotein cholesterol (HDL-C) levels in women compared with healthy volunteers. 78 This is the first report showing possible blood biomarkers for hikikomori. In addition, we have revealed that avoidant personality traits, which are strongly linked to hikikomori, are negatively associated with HDL-C and UA in men, and positively associated with fibrin degeneration products and high-sensitivity C-reactive protein in women among non-hikikomori volunteers, mainly young-adult university students.…”

“…As an initial step, we are searching for biomarkers of hikikomori using human blood by recruiting actual individuals with hikikomori . We have recently reported that individuals with hikikomori have higher avoidant personality scores in both sexes, and show lower serum uric acid (UA) levels in men and lower high‐density lipoprotein cholesterol (HDL‐C) levels in women compared with healthy volunteers . This is the first report showing possible blood biomarkers for hikikomori .…”

“…This is the first report showing possible blood biomarkers for hikikomori . In addition, we have revealed that avoidant personality traits, which are strongly linked to hikikomori , are negatively associated with HDL‐C and UA in men, and positively associated with fibrin degeneration products and high‐sensitivity C‐reactive protein in women among non‐ hikikomori volunteers, mainly young‐adult university students . High‐sensitivity C‐reactive protein and fibrin degeneration products are inflammatory markers, and HDL‐C and UA are known to have antioxidative effects .…”

“…In addition, we have revealed that avoidant personality traits, which are strongly linked to hikikomori, are negatively associated with HDL-C and UA in men, and positively associated with fibrin degeneration products and high-sensitivity C-reactive protein in women among non-hikikomori volunteers, mainly young-adult university students. 78 High-sensitivity C-reactive protein and fibrin degeneration products are inflammatory markers, 79 and HDL-C and UA are known to have antioxidative effects. 80,81 On the other hand, a nonclinical randomized control trial with healthy volunteers showed that endotoxin treatment by intravenous bolus increased blood-level inflammatory cytokinesinterleukin-6 and tumor necrosis factor-αand also increased self-reported feelings of depression and social disconnection, such as 'I feel like being alone' compared to the placebo group, 82 suggesting the importance of inflammation in social withdrawal behaviors.…”