Intermittent explosive disorder (IED) is a psychiatric condition characterized by recurrent aggressive behavior, explosive outbursts towards people and property, impaired emotion regulation and behavioral control, and it is often comorbid with other psychiatric disorders (1). IED was once considered a relatively rare disorder, but recent studies have reported diverging prevalence estimates. In the United States, while the data provided in the Collaborative Psychiatric Epidemiology Surveys showed that the prevalence of IED was in only 1.62% of the population (2), the National Comorbidity Survey in 2001 to 2003 found that the lifetime prevalence of IED was 7.3% and 5.4% when broad and narrow criteria of IED were used, respectively (3). Further, in the National Comorbidity Survey Replication Adolescent Supplement (NCS-A), researchers found that 7.8% of adolescents between the ages of 13 and 17 met the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria for lifetime IED (4). Meanwhile, for studies in other countries, the mean lifetime prevalence of IED was 3% for the broad definition and 1.6% based on the narrow criteria (1).

Due to the high aggression, anger, hostility, and poor temper control characteristics of IED, a series of studies were carried out which focused on the legal consequences of IED. They found a clear linkage between IED and criminal behavior. For example, in one federal probation jurisdiction in Midwestern United States, DeLisi studied 863 federal correction clients’ data and found that those with IED were more likely to be arrested for murder, attempted murder, interference with police, and assault (5). In Chile, Mundt found that the IED prevalence rate was 5.7% among a nationwide random sample of 1,008 prisoners in seven penal institutions (6). Similar associations also existed in the youth population. According to the data from NCS-A (4, 7), when compared to youth without IED, youth with lifetime IED diagnoses had a significantly greater probability of being arrested for burglary or theft (OR = 6.2), violent crime (OR = 11.0), or any other crime (OR = 8.8).

Over the past several decades, juvenile delinquency has emerged as a serious social problem in China (8). As China began its transformation into a market economy in the late 1970s, the problem of juvenile crimes became increasingly troublesome. In 1990, the number of juvenile offenders under the age of 18 adjudicated by the courts was 42,033, with that number rising steadily to 55,817 in 2013, thereby representing an increase of over 33% (9).

Recently, studies focused on the mental health problems of detained juvenile offenders in China have found high levels of major psychiatric morbidity, including attention deficit hyperactivity disorder (ADHD), oppositional defiant disorder (ODD) and conduct disorder (CD) (10). These findings demonstrate that juvenile delinquents in the justice system constitute a population with an elevated risk of psychiatric problems (11), showing that it is critically important to address the psychiatric needs of juvenile offenders (12, 13). One drawback of Zhou’s study was that it did not mention whether or not IED existed in this population. Since research had confirmed that IED had a comparatively high prevalence (1.7%) in metropolitan China (14), we believe that the incidence of IED in juvenile offenders cannot be ignored.

To date, few studies have investigated IED within a criminal justice context in China. In order to account for the gaps in previous literature, the present study sought to identify IED in male juvenile offenders in China. We investigated the anger-related traits and aggressive behavior in individuals with IED, psychiatric controls, and healthy volunteers in a population of juvenile offenders. The differences between the three groups were compared. We hypothesized that youths with IED would have escalated tendencies of anger and aggressive behaviors compared to those in the other two groups. We also predicted that higher anger and aggression in IED would result in different crime profiles than those in the comparison groups.

We presented the first study to investigate the phenomenon of IED in male juvenile offenders in Shanghai, the most populous city in China. Some findings in our research may contribute to the understanding of the linkage between IED and juvenile delinquency in China’s urban areas.

Using the DSM-IV criterion, previous studies had found a comparatively high prevalence of IED in metropolitan China, namely, Shen’s 1.7% in Beijing and Shanghai (14) and Duan’s 3.39% in Shenzhen (24). Our finding of 11.4% participants meeting the criteria of IED cannot be directly compared with these studies as this was not an epidemiological study. Also, we used the IED research criteria that was broader than the DSM-IV IED criteria and closer to the definition of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) (19). That said, it clearly demonstrates that the prevalence of IED in juvenile offenders cannot be ignored.

Further, research has showed that a considerable number of juvenile crime and delinquency cases in urban China were committed by adolescents who had migrated from rural areas (25). We found this phenomenon exists not only in male juvenile offenders with no DSM-IV diagnosis (58.8%), but also in the IED group (50%) and other DSM-IV diagnosis groups (66.7%). This confirms the seriousness of juvenile delinquency among the migrant population in China. Meanwhile, it also showed that IED is a problem that cannot be ignored in both juvenile offender subgroups, urban and migrants.

Individuals with IED, including adolescents, usually had significantly more major lifetime non-personality disorders, including mood disorder, anxiety, and substance dependence (7, 26–30). We also found that a considerable proportion of IED juvenile offenders were comorbid with other DSM-IV disorders, such as conduct disorder, attention deficit hyperactivity disorder, and oppositional defiance disorder; however, the proportion was not statistically different when compared to the PC group.

We did not find any mood disorders in IED participants. In fact, we did not find any participants who met the diagnostic criteria of affective disorder, mental retardation, or any other psychotic disorders during the study period. This is because offenders suffering from these disorders are usually judged as “excused,” having “extenuated criminal responsibility,” or having “no ability to serve a sentence” and thus placed in other institutions. Although depressive disorders could be secondary to their incarceration, our interviews were conducted with offenders who had been in the reformatory no more than thirty days, thus making it difficult to identify depressive episodes within the group. Without doubt, these interviewees may have had affective disorders or other psychotic disorders in the past. However, this study focused primarily on their mental status during their imprisonment. Meanwhile, the IED participants had no significant differences with the other two groups in terms of age and education levels. Thus, age, education level, and psychopathology were not included as covariates in the final analyses.

We examined levels of anger and aggression in three groups of male juvenile offenders. Although the limited sample size (32 IED participants) might lead to certain negative results, we found some difference on STAXI-2 and MOAS scores between the IED and two control groups. Compared with the HC group, the IED group showed a significantly higher anger trait as well as deficiencies in anger control-out ability. This made them more susceptible to experiencing bouts of spontaneous anger; therefore, they also reported higher state anger and anger expression-out. These findings are consistent with previous research findings where IED groups showed increased anger (31).

Studies have shown increased anger in individuals with IED relative to psychopathology control groups (26, 32) and non-aggressive personality disorder groups (33). In this research, the IED and PC groups reported similar levels of anger experience and expression except in the case of anger control ability. The lack of significant difference between offenders with IED and psychopathology control groups may be attributed to the existence of comorbidity in the IED group. The high rate of comorbidity diagnoses might explain the features found in both the IED and psychopathology control groups (26). Further, the similarities between the two groups may have resulted from the diagnostic composition of the PC group in our research. Compared to previous studies that had significant percentages of mood disorder in their PC groups (7, 26–30), our PC group was mainly comprised of those with various externalized disorders, such as ADHD, ODD, and CD, all of which were also characterized by high levels of anger experience and expression (34, 35).

Despite the similarities in anger experience between the IED and PC groups, the IED group showed higher verbal and property aggression compared to the PC and HC groups. Although physical aggression levels in the IED group were similar to the PC group, after weighting all items, the total aggression level of the IED group was the highest of all three groups. The high aggression of IED offenders in the juvenile reformatory poses a considerable risk to staff as well as to non- or less-violent prisoners. Therefore, they should be supervised with additional caution.

We hypothesized that the criminal profiles of juvenile offenders with IED would differ from those of other juvenile offenders. As predicted, participants in the IED group were more likely to be repeat offenders and perpetrators of violent crimes. These results are consistent with DeLisi’s previous findings that federal correctional clients with IED had a dramatically higher correlation with recidivism, total arrest charges, and assault-related charges (5). For individuals diagnosed with IED, their aggressive behavior was not usually intended to achieve some tangible objective like money, power, or intimidation (1). We also found that they were less prone to state money as their primary motive for crime. This might be explained by the high rate of reactive aggression and the low rate of premeditated aggression among IED subjects (36). Thus, they were more likely to be involved in violent crimes, such as rape, assault, and affray rather than planned antisocial behavior related to money, such as robbery and theft. This tendency is confirmed by the lower rate of IED participants attributing money as their motives for crime in their self-reports. This implies a discomforting situation regarding juvenile delinquents in the IED group, that is, the differences suggest the need to develop individualized crime prevention strategies for at-risk IED groups.

When interpreting our results, certain limitations should be considered. First, as a cross-sectional study, the ability to address the causality of the factors was limited. Therefore, further longitudinal studies are needed. Second, when answering questions, respondents may have tended to adhere to social norms rather than actual situations. That said, as the three groups of juvenile offenders were from the same correctional institution, there was no reason to suspect that one of the groups had more obvious misreporting issues when answering these questions, and the comparisons are probably valid. Third, the study only examined the situation of IED among male juvenile offenders in one reformatory in Shanghai. We may not be able to generalize these results to serve as indicators for female IED juvenile offenders or IED adolescents without criminal records in other cities of China. Finally, given the prevalence of depression in prisons in other countries (3, 5, 6), this may also impact the generalizability of the findings. Therefore, further research related to IED must be conducted across a broader population.

Despite these limitations, the study contributes to our understanding of IED in juvenile offenders in China. This is a problem that cannot be ignored by policymakers or mental health and criminal justice professionals. The relationship between IED with excessive anger and aggression implies that specific and individually tailored intervention approaches should be developed to correct IED juvenile offenders’ behavior in order to help prevent further crimes. Research in the near future should focus on the risk and protective factors of the disease, the creation of feasible screening and early detection strategies, and the development of effective treatment methods Manuscript Formatting.

This study was carried out in accordance with the recommendations of Research Ethical Committees at Shanghai Mental Health Center with written informed consent from all subjects. All subjects gave written informed consent in accordance with the Declaration of Helsinki. The protocol was approved by the Research Ethical Committees at Shanghai Mental Health Center (IORG Number: IORG0002202; FWA Number: FWA00003065).

YS and BX contributed to the conception of the study. YS, YQ, and MZ performed the investigation. YS and YQ contributed equally to analysis and manuscript preparation. BX reviewed and approved the final version of manuscript.

This work was supported by grants from the National Natural Science Foundation of China (81302624, PI: YQ; 81202388, PI: YS), the Shanghai three-year action plan of public health (fourth round)-senior overseas research team training program (GWTD2015509, PI: BX), and the Shanghai Municipal Health and Family Planning Commission (psychiatry) key discipline (2017ZZ02021, PI: MZ).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.