Abstract: Identifying mental distress is a complex task, particularly when individuals experience
physical symptoms. Traditional self-report questionnaires that detect psychiatric symptoms using
emotional words may not work for these individuals. Consequently, there is a need for a screening
tool that can identify both the physical and mental symptoms of mental distress in individuals
without a clinical diagnosis. Our study aimed to develop and validate a scale that measures mental
distress by measuring the extent of brain overwork, which can be extrapolated as the burden of
mental distress. In this population-based cross-sectional study, we recruited a total of 739 adults
aged 16–65 years from 64 sampling centers of a cohort in Mongolia to validate a 10-item selfreport questionnaire. Internal consistency was measured using McDonald’s ω coefficient. Test–
retest reliability was analyzed using intraclass correlation coefficients. Construct and convergent
validities were examined using principal component analysis (PCA) and confirmatory factor analysis
(CFA). The Hospital Anxiety and Depression Scale (HADS) and the abbreviated version of World
Health Organization Quality of Life (WHOQOL-BREF) were used to evaluate criterion validity.
Among the participants, 70.9% were women, 22% held a bachelor’s degree or higher, 38.8% were
employed, and 66% were married. The overall McDonald’s ω coefficient was 0.861, demonstrating
evidence of excellent internal consistency. The total intraclass correlation coefficient of the test–retest
analysis was 0.75, indicating moderate external reliability. PCA and CFA established a three-domain
structure that provided an excellent fit to the data (RMSEA = 0.033, TLI = 0.984, CFI = 0.989, χ
2 = 58,
p = 0.003). This 10-item scale, the Brain Overwork Scale (BOS-10), determines mental distress in three
dimensions: excessive thinking, hypersensitivity, and restless behavior. All the items had higher
item-total correlations with their corresponding domain than they did with the other domains, and
correlations between the domain scores had a range of 0.547–0.615. BOS-10 correlated with HADS,
whereas it was inversely correlated with WHOQOL-BREF. In conclusion, the results suggest that
BOS-10 is a valid and reliable instrument for assessing mental distress in the general population.
The scale screens for mental distress that is characterized by subjective symptoms such as excessive
thinking, hypersensitivity, and restless behavior. The current findings also demonstrate that the
BOS-10 is quantitative, simple, and applicable for large group testing. This scale may be useful for
identifying at-risk individuals who may require further evaluation and treatment for mental distress.
