The antecedents of criminality have long been of interest to criminological researchers, as well as factors that mediate the links between them (e.g., ). However, most of the existing studies on personality characteristics and abilities that contribute to the development of criminal behavior have focused on single factors in relation to offending, and integration among studies has often occurred post-hoc via logical inferences (e.g., because construct X is related to construct Y, which in turn is related to criminal behavior, an indirect effect can be logically expected). In the current study, we hence proposed and tested a theory-driven model that focuses on the interplay between narcissism, identity integration, and self-control, in the explanation of criminal behavior.
Despite numerous studies on narcissism, no consensus has been reached on a widely accepted definition of narcissism [2,3,4]. However, over the past 20 years, there has been broad recognition of the need to differentiate between different types of narcissism that can be roughly divided into narcissistic grandiosity and narcissistic vulnerability [4,5,6]. Although both subtypes of narcissism share a common deeper foundation, such as self-centeredness , they can have very different manifestations. Grandiose narcissism as a pathological characteristic manifests itself in exaggerated self-esteem, grandiosity and an unrealistic sense of superiority, as well as admiration seeking, entitlement and arrogance [4, 6, 8]. Most experts agree that grandiose narcissism is more a characteristic of the Narcissistic Personality Disorder, as defined by the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition, Section II (DSM-5; ), than vulnerable narcissism is [3, 5, 10]. In contrast, vulnerable narcissism entails pronounced self-absorbedness, low self‐esteem, hypervigilance, shyness, social withdrawal and emotional hypersensitivity [11, 12]. Recent studies have shown that grandiose narcissism is less harmful to mental health, while vulnerable narcissism is associated with psychological problems and the use of rather inappropriate emotion regulation strategies, such as aggression and repression .
In general, research suggests that narcissism is quite overrepresented in samples of violent offenders (e.g., [14,15,16,17]), and positively associated with criminal behavior [18, 19]. However, in the field of forensic psychology, researchers have only recently begun to investigate the difference between grandiose and vulnerable narcissism and no research to date has investigated how both forms differ from one another concerning criminal behavior. Yet, some indirect evidence emerges from studies on grandiose and vulnerable narcissism in relation to aggression, more specifically proactive and reactive aggression. While the results have been somewhat mixed, the available evidence suggests that narcissistic grandiosity is associated with both forms of aggression, while narcissistic vulnerability is associated only with reactive aggression (e.g., [20,21,22]). Compared to vulnerable narcissism, grandiose narcissism has also been more strongly associated with a wide variety of impulsivity-related externalizing behaviors, such as gambling , substance use , antisocial behaviors , and proactive aggression . Individuals with higher levels of grandiose narcissism may have excessive confidence in their competencies and take more risks , probably due to their excessively active reward-oriented system (e.g., ). They focus more on positive outcomes and do not estimate chances and outcomes in a realistic way . Additionally, aggression in individuals with higher levels of grandiose narcissism is usually seen as a self-enhancing strategy with the aim of restoring or enforcing a sense of superiority [29, 30]. However, there is also contrasting evidence suggesting that individuals with high narcissistic vulnerability are more likely to display aggressive behavior than individuals high on grandiosity (e.g., [31, 32]). For example, Krizan and Johar  found that narcissistic vulnerability (but not grandiosity) has particularly shown to be a powerful driver of rage, hostility, and aggressive behavior, fueled by suspiciousness, dejection, and angry rumination. The fragmented sense of the self and desperate need for external appreciation predisposes individuals with higher levels of vulnerable narcissism to experience shame about their narcissistic needs and unrestrained anger towards those who exposed their weaknesses . This, in turn, triggers “narcissistic rage” that can further promote aggressive behavior . Due to inconsistency and a scarcity of empirical evidence, additional research is needed to uncover whether and how these two subtypes of narcissism are associated with criminal behavior. Indeed, previous research has mainly focused on the link between narcissism and aggressive behavior in samples of the general population. Possible relations of different variants of narcissism with more severe forms of violent behavior (e.g., sanctioned by society) remained largely understudied.
Likewise, little is known about the mechanisms underlying the association between narcissism and criminality. According to Stern , the narcissistic individual is often attuned to what other individuals feel and think. This notion is closely related to the core aspect of identity, namely the fact that the individual is partly determined by interaction with his environment and must develop the ability to act effectively as an independent subject in that environment.
Identity refers to how a person defines the self and understands intimate relationships and social interactions with the social world. Identity formation is a process of alternating phases of ‘crisis and commitment’ that occur especially during adolescence . Identity integration can be defined as a coherence of identity; the capacity to see oneself and one's life as stable, integrated and purposive . In contrast, identity diffusion is characterized by a lack of normative commitment and reflects difficulties in maintaining a relatively constant set of goals . Notably, identity diffusion does not occur in a vacuum; rather, it is an important feature that is associated with various personality dysfunctions and characterizes personality pathology [38,39,40]. According to the DSM-5 Section III , significant impairments in self-identity (e.g., unstable self-image, inconsistencies in values, goals, and appearance) and interpersonal functioning (e.g., being insensitive to others, inconsistent, detached, or abusive style of relating) are the main characteristics of personality disorders. In particular, identity diffusion (i.e., incoherent self-image, self-fragmentation) is one of the core components of a narcissistic personality disorder [41, 42]. Narcissistic individuals show excessive dependency on others for identity; they need constant external support and attention to maintain their self-esteem, and self-esteem problems often shift between inflated and deflated self-appraisal .
Despite theoretical elaboration of the role of identity in narcissism, there is little empirical research on the association between narcissism and identity integration. However, available evidence suggests that narcissistic traits [41, 44], and in particular narcissistic vulnerability [39, 40, 45], are associated with higher identity instability (i.e., a weak sense of the self). For example, Dashineau et al.  found that narcissistic vulnerability was associated with all forms of dysfunction (e.g., well-being, self-control, and everyday life tasks), while grandiosity was associated with specific deficits in interpersonal functioning. However, after accounting for shared variance in vulnerability, grandiosity was not associated with most aspects of poor functioning and was positively associated with better functioning in some areas, such as life satisfaction. Similarly, Huxley et al.  found that vulnerable narcissism was associated with impairment in self- and relational functioning, while grandiosity predicted higher self-functioning. More research is needed to investigate how both grandiose and vulnerable narcissism are associated with identity integration.
Furthermore, it has been shown that identity diffusion can result in feelings of emptiness, deviant behavior and superficiality, or other maladaptive outcomes, such as poor impulse control [41, 42]. In the identity-value model, Berkman et al.  proposed that identity plays a crucial role in self-control. By its definition, identity is a relatively stable mental representation of personal and intrapersonal values, priorities, and roles. Therefore, individuals are more prone to associate their identity with long-term goals than with short-term impulses. According to this model, self-control is defined as a decision-making process that compares the subjective value of two options and selects the option with the highest value . Therefore, individuals with more integrated identity are better at making choices that are relevant to their long-term goals over short-term impulses, meaning they are better at self-control.
Self-control is conceptualized as the capacity to tolerate, use and control one’s own emotions and impulses . Research has shown that the degree of self-control is positively associated with adaptive correlates in various life domains, such as academic and professional success, healthier and more sustainable intimate relationships, closer social networks, greater self-awareness, empathy, and more proactive health behaviors (e.g., regular medical check-ups; ). In contrast, a lack of self-control is linked to a wide range of antisocial and deviant behaviors [48,49,50,51], and a variety of negative life outcomes, such as criminal victimization, poor health, and financial difficulties (e.g., [52,53,54]).
According to the general theory of crime , a lack of self-control is the main factor behind all criminal acts [56, 57], although in this theory self-control was conceptualized in broader terms as “the differential tendency of people to avoid criminal acts whatever the circumstances in which they find themselves” [55 p87]. A lack of self-control was thus characterized by impulsive behavior towards others, physical risk-taking and shortsightedness, and can give rise to criminal acts in interaction with situational opportunities .
In sum, there is evidence that grandiose and vulnerable narcissism contribute to disintegrated identity and criminal behavior. In addition, there are indications that identity diffusion is directly associated with criminal behavior and that this association is mediated by self-control. Several studies have reported bivariate associations between pairs of these constructs, as previously reviewed. However, to our knowledge, no studies so far have investigated whether identity integration and self-control sequentially mediate the association between grandiose and vulnerable narcissism and criminal behavior.