Abstract: Objective To explore the applied value of mismatch negative （MMN） in evaluation of severity of mental disorders due to traumatic brain injury. Methods Thirty-five patients（case group） that conform to the diagnostic criteria of organic （traumatic brain injury） mental disorder in ICD-10 Classification of Mental and Behavioural Disorders criteria were selected. Twenty-four healthy subjects （normal control group） that matched the case group in terms of gender, age composition ratio and educational level were selected. All subjects were evaluated by Activity of Daily Living Scale （ADL） and Social Disability Screening Schedule （SDSS） and then examined by Event-Related Potential （ERP）. A statistical analysis of the data was made by SPSS 22.0 software. Results The 32 patients and 24 normal control subjects completed the study. The scores of ADL and SDSS were significantly higher in the case group than in the normal control group （P<0.05）. The latency of Fz, FCz, Cz and Pz in the case group was significantly longer than that in the normal control group （P<0.05）. In the case group, the latency of Fz, FCz, Cz and Pz was positively correlated with the scores of ADL and SDSS （P<0.05）. The equation can be well fitted with the scores of ADL and SDSS. The latency and amplitude of Fz, FCz, Cz and Pz were used as concomitant variables and whether or not the subjects had mental disorders due to traumatic brain injury as dependent variables. Conclusion The latency of MMN can be used as an indicator in potential evaluation of the severity of mental disorders due to traumatic brain injury, which means that the longer the latency of MMN is, the more severe mental disorders due to traumatic brain injury may be. The combined application of ADL, SDSS and MMN can be an objective indicator in preliminary judgment of mental disorders due to traumatic brain injury.

Key words: forensic psychiatry, mental disorders, brain injuries, mismatch negative, event-related potential