Non-suicidal self-injury and its relation to suicide through acquired capability: investigating this causal mechanism in a mainly late-diagnosed autistic sample

Abstract

Background Non-suicidal self-injury (NSSI) has been linked with a higher risk of suicide attempts in autistic and non-autistic people. In the general population, NSSI may confer acquired capability for suicide by eroding one’s fear and avoidance of pain and death. The present study aimed to explore acquired capability as the mediator of increased suicide risk conferred by NSSI in autistic and non-autistic adults. Methods Autistic and non-autistic adults (n = 314, n = 312) completed an online survey exploring lifetime suicide attempts, experience with NSSI, and acquired capability for suicide. We explored relationships between lifetime incidence of NSSI and lifetime suicide attempts via three facets of acquired capability (pain tolerance, reduced fear of death, and mental rehearsal of suicide). In self-harming participants (224 autistic and 156 non-autistic), we explored whether particular types and features of NSSI might be especially associated with capability and through that with suicide: namely engagement in scratching, cutting, and self-hitting, and engaging in more numerous forms of NSSI. Results While a higher frequency of NSSI was associated with all three facets of acquired capability, only reduced fear of death and mental rehearsal of suicide mediated an indirect relationship with lifetime suicide attempts. NSSI also directly predicted more numerous suicide attempts. Autistic people tended towards reduced fear of death and mental rehearsal regardless of NSSI status. Among self-harming autistic and non-autistic participants, cutting and an increased number of NSSI behaviours were associated with lifetime suicide attempts directly and indirectly via acquired capability. In both groups, self-hitting was associated with lifetime suicide attempts only via acquired capability. Limitations Our cross-sectional methodology negates inferences of directionality. While we controlled for age, our samples were poorly matched, with the autistic group two times older on average. The autistic sample, predominantly late-diagnosed, female and highly qualified, were unrepresentative of the whole autistic community. Conclusions Our data suggest that acquired capability, as measured herein, is an incomplete explanation for the association between NSSI and suicide risk. A broader construct with stable and transient facets may offer greater explanatory power, but it is probable that other variables explain or provide additional means through which this association arises.

Autism in adult psychiatric out-patients: self-reported suicidal ideation, suicide attempts and non-suicidal self-injury

“…The overlap between suicidality and NSSI that we found is in line with a recent study on an adult psychiatric population 33 and a recent study on an adult ASD population. 23 The most common NSSI methods were hitting oneself, picking at wounds, cutting or carving oneself and biting oneself. This is in line with other studies of adults in both psychiatric and general populations, 49,56 although the method of hitting oneself was more common in our study group.…”

“…22 NSSI has been reported as predictive of both the occurrence of suicide attempts and of more numerous suicide attempts in adults with autism, who, compared to adults without autism, have also been suggested to report a reduced fear of death and more mental rehearsal of suicide, which in turn was a mediating factor for lifetime suicide attempts. 23 NSSI has been defined as 'the direct, deliberate destruction of one's own body tissue in the absence of suicidal intent'. 24 An important difference between NSSI and other forms of self-injurious behaviours is that people who engage in NSSI do not intend to end their own life, and NSSI is often performed without present suicidal ideation.…”

“…28 NSSI among adults with autism without intellectual disability has only been reported in a small number of studies. Three (online) surveys 22,23,29 have suggested lifetime prevalence rates of NSSI at 50-74% in adults with autism; two of the surveys 22,23 found lifetime prevalence rates of NSSI to be higher in adults with autism than in adults without autism. The functions of, or reasons for engaging in, NSSI in adults with autism have so far been reported to be emotional regulation, [30][31][32] but also in some cases sensory stimulation.…”

The biosocial correlates and predictors of emotion dysregulation in autistic adults compared to borderline personality disorder and nonclinical controls

“…Indeed, similar to findings in BPD and in the general population [ 14 , 22 ], ED has been associated with self-harm with or without suicidal intent in ASC [ 19 , 21 ]. Interestingly, akin to BPD [ 22 ], self-harm and suicidal behaviours have also been found to be strongly linked in ASC [ 14 , 23 ]. This suggests that ED is a risk factor for suicidality and self-harm in ASC, and that autistic people may develop capability for suicide through self-harm [ 14 , 23 ].…”

“…Interestingly, akin to BPD [ 22 ], self-harm and suicidal behaviours have also been found to be strongly linked in ASC [ 14 , 23 ]. This suggests that ED is a risk factor for suicidality and self-harm in ASC, and that autistic people may develop capability for suicide through self-harm [ 14 , 23 ]. Autistic women in particular have been reported to be at greater risk of developing severe ED compared to autistic men [ 24 – 26 ], which suggests that gender-related factors might be involved in ED in ASC [ 27 ].…”