Nonsuicidal self-injury (NSSI), the destruction of one’s own body tissue without intent to die, is highly prevalent among adolescents with lifetime prevalence rates between 18 and 39% [
1,
2]. In a meta-analysis examining functions of NSSI, Taylor and colleagues [
3] identified intrapersonal functions (66–81%), especially emotion regulation (63–78%), being the most frequent function, followed by interpersonal functions (33–56%). Interpersonal factors are relevant in initiating and maintaining NSSI, as interpersonal difficulties are often reported as triggers for emotional dysregulation [
2]. In this context, NSSI can be understood as a dysfunctional emotion regulation strategy to deal with interpersonal stressors among other stressors associated with NSSI.
The development of emotion dysregulation—as an intrapersonal consequence of NSSI—through the interplay between an invalidating family environment and the child’s emotional reactivity has been described by the biosocial theory developed for Borderline Personality Disorder [
6]. As NSSI is an emotion regulation strategy that is also a symptom of Borderline Personality Disorder, and also an adverse parent–child relational experience has been shown to predict greater emotion dysregulation, which in turn is associated with NSSI [
7], and invalidating family environment might also apply to adolescents engaging in NSSI. Family interactions are reciprocally influenced by adolescents’ and parents’ behavior [
8] and were found to be heavily shaped by conflict-ridden interaction patterns of adolescents who engage in NSSI and their mothers [
9]. Intrapersonal and interpersonal consequences influence each other. Studies have suggested a mediating role of adolescent emotional regulation difficulties and poor coping strategies in the relationship between invalidating caregiving environments and NSSI [
7,
10,
11], thus supporting Nock’s [
4,
5] model of NSSI. Therefore, it seems to be of importance to examine the parent–child relationship in families with adolescents engaging in NSSI.
Expressed emotion is a measure of the family environment that describes the level of criticism, hostility, and emotional involvement that a relative expresses toward a family member [
12,
13]. High expressed emotion predicts treatment discontinuation, relapse, and unfavorable disorder trajectories of various mental disorders in children, adolescents, and adults [
14‐
17]. Maternal criticism appears to be associated with internalizing and externalizing disorders in adolescents, and emotional overinvolvement with internalizing problems [
16]. However, there is also evidence that several of the scoring criteria for emotional overinvolvement have been adapted from parents and their adult children diagnosed with schizophrenia and might not be appropriate for parents of children with emotional and behavioral problems [
18]. Maternal criticism, on the other hand, is a valid proxy for children’s psychopathology and an index of problematic parent–child interactions [
19]. There is evidence that psychological disturbances contribute to increased expressed emotion and are also simultaneously maintained by expressed emotion [
20]. High expressed emotion exhibited by parents is also related to the presence and frequency of suicidal ideation and plans, suicide attempts, and NSSI in youth [
21]. On studying the relationship between expressed emotion and NSSI, parental criticism was associated with NSSI [
21,
22], whereas emotional overinvolvement was not [
21]. The association between parental criticism and NSSI was particularly strong among adolescents who were self-critical [
21]. Further, maternal criticism was more strongly related to NSSI in girls than in boys [
22]. Results relying on adolescents’ perceived levels of parental expressed emotion indicated that adolescents and young adults with a history of NSSI perceived their parents as less emotionally supportive, more intrusive, more irritating, and more critical than those without NSSI [
23]. Similar results were found in adults engaging in NSSI [
24]. In addition, adolescents’ self-criticism played a mediating role in the relationship between perceived parental expressed emotion and NSSI [
23,
25]. Taken together, results indicate that the family environment of adolescents with NSSI seems to be characterized by high levels of criticism. Parental criticism may increase self-criticism in adolescents and thus the risk for NSSI [
23]. However, the relationship between high expressed emotion (especially criticism) and NSSI in families of adolescents engaging in NSSI needs to be further explored. Previous research examining the link between expressed emotion and NSSI has focused on observed (coding of speech samples) and perceived (various self-report measures) levels of parental expressed emotion, neglecting the dyadic aspects of relationships. The conceptualization of expressed emotion as a unidirectional construct from parent to child may present an incomplete picture [
26]. Further, a recent review on expressed emotion within families discusses its possible role in the transgenerational transmission of mental disorders [
27].