The Effect of Non-Suicidal Self-Injury on Suicidal Ideation: A Real-Time Monitoring Study

Abstract

Clinical and empirical reports suggest that individuals use non-suicidal self-injury (NSSI) not only to ameliorate dysphoria, but to curb suicidal ideation (SI) or avoid suicidal behavior. To date, however, no study has quantitatively assessed whether NSSI leads to short-term reductions in SI. Using real-time monitoring over seven days in a sample with borderline personality disorder (BPD), we found evidence that NSSI is followed by reductions in SI in the subsequent hours. This suggests that NSSI may serve as an effective, albeit maladaptive, coping strategy for suicidal states. These findings have important implications for the management of suicide risk and self-harm.

Introduction

Non-suicidal self-injury (NSSI), the intentional self-infliction of bodily harm without apparent suicidal intent, is a potent risk factor for suicidal ideation (SI) and behavior^[1]. While NSSI and suicidal behavior (SB) are distinct constructs, both forms of deliberate self-harm frequently co-occur. NSSI and SB share key instrumental functions, such as escape from aversive internal states, reducing dysphoria, or communicating distress^[2]. Some individuals also report engaging in NSSI to ameliorate suicidal thoughts or urges ^[2], a possible byproduct of NSSI’s regulating effect on mood. In an adolescent sample, nearly half of self-harmers reported using NSSI to diminish the urge to attempt suicide^[3]. However, evidence of NSSI’s mitigating impact on SI is limited to subjective reports of its perceived effectiveness^[4], and it remains unclear whether in fact NSSI is associated with subsequent reductions in SI. This is important to establish, since the success of NSSI’s anti-suicidal function may encourage recurrent self-injury.

Despite NSSI’s perceived effectiveness in mitigating suicidal states, self-harming suicidal individuals have demonstrably higher long-term risk of SB relative to non-self-harming suicidal individuals^[1]. Elevated suicide risk amongst self-harmers is consistent with the interpersonal theory of suicide^[5], which suggests that repeated self-harm may promote a capability for suicide over time by habituating individuals to the fear of physical pain or injury that might otherwise discourage SB. In the short-term, however, NSSI may serve to lower acute suicide risk, consistent with findings that individuals with SI who self-harm take longer to transition to suicide attempt compared to non-self-harming suicidal individuals^[6]. As yet, the functional relationship between NSSI and suicidal states—particularly its short-term effect on SI—is not well characterized, due in part to methodological challenges inherent in observing these experiences in research settings. However, recent advancements in smartphone-based technology have stimulated new research using ecological momentary assessment (EMA) to study NSSI in real-world contexts^[7]. EMA involves repeated, real-time sampling of participants’ thoughts and behaviors over a discrete period, overcoming issues of recall bias, forgetting, or post-hoc reasoning that influence retrospective reporting.

Prior EMA studies have assessed triggers and consequences of NSSI, largely concentrating on NSSI’s affective dynamics^[7], but none to date have quantitatively evaluated NSSI’s real-world effect on SI. We sought to address this gap by using real-time monitoring of NSSI and SI over seven days in adults with borderline personality disorder (BPD), a clinical population with exceptionally high rates of NSSI, SI, and SB^[8]. We hypothesized that episodes of NSSI would lead to a reduction in SI in the subsequent hours.

Method

Recruitment.

Eighty-two participants were enrolled in an NSSI intervention trial and completed EMA during the pre-randomization, pretreatment stage. All participants provided written consent after receiving a detailed description of study procedures. Protocols were approved by the Institutional Review Board at New York State Psychiatric Institute and complied with up-to-date ethical standards stipulated in the Helsinki Declaration. Eligibility criteria included a DSM-5 BPD diagnosis, current SI, and history of SB and/or NSSI. See Stanley, Martínez-Alés^[9] for a detailed description of study criteria and clinical assessment measures.

EMA procedure.

Using smartphones or digital devices, participants completed EMA six times daily within a 12-hour wake period for seven consecutive days. Prompts occurred at random intervals within 2-hour epochs. SI and self-harming behaviors were assessed at each epoch, and self-harm was rated for suicidal intent. Participants rated nine SI items adapted from the Scale for Suicidal Ideation^[10], inquiring how strongly they experienced thoughts or urges to die by suicide on a 0–4 Likert scale. A full description of EMA queries is reported elsewhere^[9].

Statistical Analysis.

EMA SI items were summed into a time-varying SI score (range: 0–36). Change in SI at a given time t was measured as the difference in SI at time t and the epoch immediately preceding it (t-1), for same-day observations. Mixed-effects logistic (NSSI) and linear (SI) models featured subject-level random intercepts and AR(1) within-subject correlation structures.

Results

Sample Description.

Participants (N=82) were predominantly female (91%) and White (57%), with an average age of 29.4 ± 9.5 years. All participants had a history of either NSSI (n=76, median=38 episodes) and/or suicide attempt (n=59, median=1). See Stanley, Martínez-Alés^[9] for a complete sample characterization.

EMA Responses.

We obtained a mean of 27 responses per participant (64% completion rate). Ninety-one percent of epochs had a non-zero level of SI (SI Median (IQR)=7 (4,11)); 37 participants (45%) reported one or more NSSI episodes (Median (IQR)=0 (0,2)).

SI Before and Concurrent with NSSI.

We examined change in SI prior to NSSI (in addition to following NSSI) to provide a broader view of NSSI’s temporal relationship to SI. Mixed-effects models indicated that a one-point increase in SI change from the epoch prior to the epoch concurrent with NSSI (t-1 to t) predicted 15.2% greater odds of NSSI (OR (95% CI)=1.15 (1.11,1.19), p<.001). Total SI concurrent with NSSI (t) predicted greater likelihood of NSSI in that epoch (OR (95% CI)=1.15 (1.12,1.17), p<.001).

SI Following NSSI.

Participants reported a mean 1.77-unit reduction (i.e., change) in SI following epochs with NSSI, which significantly differed from the mean 0.05 unit increase in SI reported following epochs without NSSI (See Table 1). To assess whether SI change following NSSI may be related to SI severity, we compared mean SI following epochs with or without NSSI; there were no significant differences.

Table 1.

Separate single-predictor linear models of 1) the effect of NSSI on mean SI in the following epoch, and 2) the effect of NSSI on change in SI in the following epoch.

	NSSI in Prior Epoch		No NSSI in Prior Epoch		Difference
Response Variable	Estimate	SE	Estimate	SE	Estimate	SE	df	t-value	p-value
Mean SI	17.72	0.79	17.69	0.66	0.03	0.45	2104	0.06	0.954
SI Change	−1.77	0.54	0.05	0.1	−1.81	0.56	1559	−3.26	0.001

Discussion

This study is the first to provide evidence for the real-world effect of NSSI on suicidal ideation. Using EMA real-time monitoring in a BPD sample, our findings demonstrate that NSSI episodes are preceded by increases in SI and followed by reductions in SI. The short-term ameliorating effect of NSSI on SI presents a challenge to suicide prevention since it may encourage repeated self-harm, which in turn significantly escalates risk for future suicidal behavior^[1]. In fact, NSSI is one of the most robust risk factors for suicide, surpassing even prior suicidal behavior as a predictor of suicide attempts^[11]. Early intervention for NSSI may be important to reducing the reinforcing effects of self-injury that contribute to long-term suicide risk. Additionally, our findings suggest that NSSI interventions should address the potential negative consequences of engaging self-injury as strategy to reduce SI, and provide alternative means of regulating suicidal thoughts and urges to self-harm.

For suicidal populations, NSSI may be more likely to function as a coping mechanism for suicidal urges than other common purposes for NSSI, since both behaviors reflect a wish to escape intolerable negative affect. NSSI, however, is oriented toward the temporary alleviation of distress, perhaps as a compromise for the permanent solution that suicide represents^[2]. Self-harm may therefore serve as a stepping stone to suicide attempt, and in fact typically emerges prior to first suicide attempt^[6]. When applied to the current sample, risk of transitioning to suicide attempt may be greater for BPD compared to non-BPD individuals, since NSSI in this population begins earlier in life and persists later into adulthood. Indeed, BPD individuals have an alarming 10% rate of completed suicide^[9] and 84% rate of nonfatal SB. These statistics highlight the importance of regarding NSSI in BPD individuals who present for care at mental health or emergency department settings as an important indicator of potential suicide risk.

This study was not able to determine whether NSSI’s mitigating impact on SI is a consequence of decreased dysphoria due to NSSI’s regulatory effect on mood, since EMA sampling occurred only once every two hours. This precludes the ability to determine whether reductions in negative affect preceded reductions in SI. Nevertheless, our findings provide the first real-world evidence that NSSI is associated with reductions in short-term SI. This association may reinforce use of NSSI to manage suicidal states, thus promoting continued self-harm and elevated suicide risk. Future research might seek to clarify mediators of the relationship between NSSI and short-term reduction in SI, and their relationships to long-term suicide risk.

Relevance Statement.

We find that individuals with suicidal ideation (SI) who engage in non-suicidal self-injury (NSSI) experience quantifiable reductions in SI in the hours following self-harm. The ameliorating effect of NSSI on SI may reinforce a pattern of recurrent self-harm, a significant risk factor for suicidal behavior. These findings suggest that screening for suicide risk should incorporate assessment of NSSI. Interventions targeting NSSI should include alternative approaches for coping with suicidal ideation and urges in order to prevent a reliance on NSSI for management of suicidal states.

Data Availability Statement:

Data available on request from the corresponding author due to privacy/ethical restrictions.