Our study had several important methodological features, including multiple self- and peer-reported measures of neuroticism. Peer-reported neuroticism had convergent and discriminant validity with internalizing psychopathology and substance use disorders. Moreover, peer measures increased the construct validity of neuroticism. The higher-order neuroticism factor, compared with the self-report factor, had higher convergent validity but similar discriminant validity. We showed a medium-to-large correlation between self- and peer-reported neuroticism, suggesting there is common variance between self- and peer-report, but also suggests that substantial variance is unshared. Peer-report methodology can provide incremental information not available by self-report, and it is less likely to be contaminated by certain biases. Therefore, peer-reported data should be considered for inclusion in future studies. Because self- and peer-reported neuroticism do not completely overlap, they may have different external correlates.
