The Social_Mistrust_Scale (SMS) is FREE for all research use but the author would like for your to ask for permission first.
The Social Mistrust Scale (SMS; Wong, Freeman, & Hughes, 2014) is a 12-item child-appropriate measure of child-reported suspiciousness. Items are scored on a 3-point scale: no , sometimes , and yes  and respective items are summed to create three distinct yet inter-correlated factors: Home mistrust, School mistrust, and General mistrust (reverse coded) of others. Summing all items creates a total score out of 24 where a higher score denotes higher levels of social mistrust.
Reliability and Validity
To date, the SMS has been administered to five independent samples of children and adolescents (8 to 14 years-old) from the UK, Hong Kong, and Mainland Chinese (Twins). Prevalence rates, factor structure, convergent validity, and heritability estimates (Zhou, Wong et al., 2018) of childhood social mistrust has been documented here. The Chinese translated version of the SMS is available upon request.
Wong, K.K., Freeman, D., & Hughes, C. (2014). Suspicious young minds: paranoia and mistrust in 8- to 14-year olds in the UK and Hong Kong. British Journal of Psychiatry, 205, 1-9.
Zhou, H.Y., Wong, K.K., Shi, L.J., Cui, X.L., Qian, Y., Du, Y.S., Lui, S.S.Y., Luo, X.R., Cheung, E.F.C., & Chan, R.C.K. (2018). Suspiciousness in young minds: Convergent evidence from non-clinical, clinical and community twin samples. Schizophrenia Research.