The Social Mistrust Scale (SMS) is FREE to use for all research purposes. However, I ask that you email for permission first.
The 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.
To date, the SMS has been administered in over 5,500 children and adolescents between the ages of 7 and 18 years-old in the UK, Hong Kong, and China.
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.