Overview of the study findings

The present study found a partial mediating effect of psychopathy on the relationship between ACEs and past-year self-harming behaviours. However, the mediation effect was complete in relation to lifetime self-harming behaviours. Overall, the mediating effect of psychopathy on the relationship between total ACEs and self-harming behaviours almost mirrored that of individuals who had experienced child abuse and incarceration of a household member. Other interesting findings from the study and the implications are discussed below.

Prevalence of psychopathy, distribution of PCL-R score, and the associated factors

Out of the 590 eligible individuals who were included, approximately 7.49% had psychopathy based on a cut-off score of 30. The prevalence rate in the present study is higher than the pooled prevalence rate of 1.2% reported in a meta-analytic review of studies conducted among the general population using the same tool and cut-off score [29]. However, the prevalence reported in the current study is lower than the pooled prevalence of 27.8% for psychopathy from studies conducted among individuals in the correctional system charged with homicide [25]. The differences in the rates of psychopathy between our study and the cited studies may be attributed to the differences in the characteristics of the study populations. For example, it is possible that forensic patients (included in our study) are individuals most likely to be diagnosed primarily with severe mental illness [19], and fewer of them may have psychopathy compared to offenders involved in homicide. Similarly, a lower PCL-R mean score was observed in our study participants compared to individuals convicted of homicide (15.26 ± 7.42 vs. 21.2 ± 5.3) [25]. While the prevalence of psychopathy in our study is lower compared to the correctional population with homicide, the results were close to those of the general population [7, 29].

In keeping with the findings documented in previous meta-analytic studies, the mean score of the measure (PCL-R) for psychopathy in the present study was higher among males than females [29, 30]. A detailed explanation for this difference has been described by Beryl et al. [30]. The present study also found that the average PCL-R scores decreased with an increase in the level of education. This may be attributed to the idea that antisocial behaviours, disregard for social norms, and impulsive behaviours that are associated with psychopathy may lead to poor academic performance and, in turn, lower academic achievements [31, 32]. In addition, psychopathic characteristics may lead to higher chances of involvement with the criminal justice system, which may negatively affect an individual’s progress in school. Contrary findings have been recorded for certain professions, especially in business, where individuals with higher mean scores on the PCL-R were high academic achievers [31, 33]. The mean score for psychopathy was also higher among individuals with two interlinked conditions, i.e., substance use history and comorbid medical conditions [34], a relationship that may be attributed to the complicated lifestyle (e.g., not adhering to rules and instruction, such as failure to stay away from dangerous substances or follow medication adherence often adopted by individuals with higher psychopathic traits.)

Prevalence of ACEs and the associated factors

Over 60% of the study participants experienced ACEs, with most experiencing child abuse. The high prevalence rate of ACEs in the present study is similar to the findings among forensic populations in other parts of the globe, such as Sweden (57.2%) [8], USA (79.4%) [35], and UK (82.8%) [9]. It is important to note that the average number of reported ACEs events (1.22±1.30) was lower in this sample than in previous studies that employed the same method of identifying ACEs, such as 2.63±2.3 among a sample of 157 forensic psychiatric patients from the USA [36]. The difference may be attributed to the smaller number of ACEs identified in the current study (8), while many studies identify more.

The mean for the total number of ACEs experienced decreased with an increase in the education level, a finding consistent with other previous studies [37]. A plausible explanation may be that ACEs have been linked with impairment of cognitive function, working memory, attention, and language acquisition, which can lead to poorer academic performance [38]. However, it is important to note that some studies have reported no significant impact of ACEs on academic performance, which are findings attributed to individuals’ resilience and protective factors [39]. Similar to individuals who scored high on PCL-R, those with a higher mean number for ACEs had a history of substance use and suffered from a comorbid medical condition.

In the present study, an increase in ACEs correlated positively with PCL-R score. Existing literature consistently reported a link between ACEs and psychopathy [13]. These findings further support the notion that a high number of individuals with ACEs are more likely to have a significantly higher PCL-R score, except for individuals with ACE resulting specifically from intergeneration abuse and staying in a household with an individual diagnosed with mental illness before the age of 18 in this study.

Prevalence of self-harming behaviours and the associated factors

Among the study participants, approximately 5% had self-harming behaviours during the reporting years under study. This prevalence is several folds lower than reported in other forensic settings, including Sweden, the USA, and the UK, with prevalence ranging between 36.0% and 68.4% [9, 11, 17, 18, 40]. The low prevalence in the present study may be attributed to the nature of the sample population, made up mainly of individuals with psychopathy based on PCL-R evaluation. By practice, not every forensic psychiatric patient in Ontario is assessed using a PCL-R. Those deemed with high suspicion of having psychopathy get assessed, thus skewing the number that are more likely to screen positive for psychopathy or score highly on the PCL-R. These individuals with higher scores may score highly on both Factor 1 and 2 of the PCL-R. With individuals who met the criteria for psychopathy in the present study having experienced fewer incidences of self-harming behaviours than those who didn’t. We speculate that the influence of scoring highly on the specific PCL-R items that load on factor 1 (i.e., involving items related to interpersonal and affective deficits of psychopathy, including shallow affect, superficial charm, manipulativeness, lack of empathy), which are associated with less self-harming behaviours [16] led to the lower prevalence observed.

Mediating role of PCL-R score on the effect of ACEs on self-harming behaviours

The present study found a partial mediation role of PCL-R score on the effects of total ACEs on past year self-harming behaviours after controlling for other covariates. This indicates that other variables may be explanatory of the effects of ACEs on self-harming behaviour in addition to PCL-R score, such as biological factors like inflammation [41], an aspect that is outside the scope of the present study. Consequently, further research is warranted to fully understand the interplay of psychopathic traits and other putative factors on the relationship of ACEs with self-harming behaviours among forensic patients. Again, the partial mediation may be due to the tool used (i.e., PCL-R), which may not capture all aspects of psychopathy or personality that are relevant to self-harm. For example, some researchers have argued that the PCL-R may not be adequate to measure affective and interpersonal dimensions of psychopathy, such as callousness, narcissism, or Machiavellianism, that may relate to self-harm [42]. On the other hand, the mediating relationship of PCL-R on the effects of ACEs on self-harming may potentially be since individuals who have experienced ACEs may develop psychopathic traits as a maladaptive coping mechanism [13]. The psychopathic traits (captured by the PCL-R) may, in turn, increase the likelihood of engaging in self-harming behaviours as a form of emotional regulatory mechanism or to exert control [16, 22].

Based on sensitivity analysis, psychopathy loaded higher as a mediator for self-harming behaviours for individuals with ACEs from living in a foster house, having a family member previously incarcerated, and having a history of child abuse. These findings may be explained by several factors, including inherited gene influence (genes that influence psychopathy and or involvement in self-harming behaviours), adopting of maladaptive coping style, and vulnerability index.

Our study findings among individuals with a family member incarcerated before 18 years may be related to the interplay of genetics (inheritance) and learning of maladaptive coping strategies the family member who ended up incarcerated used. This nature and nurture effect may lead to using self-harming behaviours as a coping skill, developing psychopathic traits, and ending up within the correctional justice system. Research has implicated genetic links for psychopathy among multiple family members [43].

Individuals who stay in a foster home may be exposed to various forms of childhood trauma (e.g., child abuse, neglect, instabilities, etc.) that may impact their emotional development and attachment security [44]. Consequently, they are vulnerable to developing emotional dysregulation and psychopathic traits (such as lack of empathy, remorse, or guilt) that are precursors for risky behaviours [20]. Due to the emotional dysregulation and inadequate development of coping skills among these children, some may use self-harming behaviours to cope with negative emotions, express anger or frustration, seek attention or validation, or manipulate others [20]. In addition, individuals who go through the foster care system may have poor social support and limited access to quality mental health services for children. Implicitly, they are isolated, helpless, and hopeless, and engaging in self-harming behaviours becomes more likely as a coping mechanism. There are several potential explanations for the complete mediating effect of psychopathy on the linkage between being in foster care and self-harming behaviours. For example, some individuals in foster care may have brain damage from encountering severe life experiences while in the system [44] and develop psychopathic traits [45] that increase their vulnerability to engage in self-harming behaviours [46].

Limitations

The following limitations should be considered in interpreting these study findings: (1) the individual facets of the PCL-R were not captured and used in the current analysis despite their strong and unique relationship with the variables assessed. Future studies should explore the interplay of the PCL-R facets on the relationship of ACEs with self-harming behaviours so that a targeted approach can be designed to mitigate the effects of such specific items as part of the interventions to reduce self-harming behaviours; (2) Self-harm was based on witnessed and reported incidents. This may be affected by the quality of information captured in the ORB report, and under-reporting of the incidents is possible; (3) The cross-sectional study design also limits inferences on causality, and a more robust prospective design should be employed in future studies, and (4) There is the likelihood of the introduction of systematic bias in the study since the individuals who are selected to have a PCL-R are dependent on clinician judgment, institutional policy, or requirement for ORB annual hearing. These may leave out some individuals who may score differently on the PCL-R, potentially leading to an altered picture of the mediating relationship captured. Lastly, despite the popularity of the use of the PCL-R tool among forensic psychiatry patients in Ontario, no available data has validated its use among patients with antisocial personality disorder, whose presentation and etiology may be similar to psychopathy [47]. Yet, they may pose varying risks of self-harming or a history of having been exposed to ACEs.

Conclusions

Among forensic patients in Ontario, psychopathy plays a mediating role in the effects of ACEs on engaging in self-harming behaviours. This role is experienced mainly by individuals who had ACEs involving child abuse, incarceration of a household member, and having lived in a foster home. For effective intervention to reduce self-harming behaviours, adequate attention should be given to the effects of identifiable mediators. Further studies are recommended to explore the interplay of specific factors or items of PCL-R on the risk attributable to ACEs for incidents of self-harming behaviours in the forensic population.