Non-suicidal self-injury (NSSI) is often misunderstood and wrongly believed to be suicidal. While both are a form of harm against the self, consequences and functions differ. But non-suicidal self-injury can occur along with suicidal thoughts, and even increase the risk for suicide. Research has found that NSSI triples the risk for suicidal thoughts or behaviors1. It is therefore important to understand the connection between NSSI and suicide.
Difference between NSSI and suicide
Non-suicidal self-injury and suicidal behaviors are two forms of self-harm that shares some similarities, such as a frequent prevalence of depression, substance use disorder, emotional distress and a dysregulation of serotonin2.
Yet, the two behaviors remain different. People who engage in NSSI do not have suicidal intentions at the very moment they self-injure, and use methods with low lethality to harm themselves3. NSSI thoughts tend to occur more frequently, last a shorter amount of time and be more intense than suicidal thoughts4.
But it is important not to consider people who self-injure as free of any suicide risk. While NSSI is not suicidal, some people still report suicidal ideation5 and self-injury can be a way for them to cope with and regulate those suicidal thoughts2, 6. It can also reach a point where it does not work as a coping mechanism anymore and lead to suicide attempts2.
Increased risk for suicide
Research has found that non-suicidal self-injury appears to be a particular risk factor in itself, as it was found to be linked to suicidal behaviors even without the influence of other factors such as depression, hopelessness, poor family functioning or borderline personality disorder3. Yet, not everyone who self-injures will experience suicidal thoughts or commit suicide. Some signs can indicate higher risk for suicide and it is important to identify them to better target those in need.
- FREQUENCY: Higher frequency in self-injury is associated with increased risk for suicidal behaviors1, 7, 8 and more suicide attempts3. Risk for suicidal behavior is at its highest between 11 and 50 episodes of self-injury, after which the risk declines2.
- NUMBER OF METHODS: Those who use more methods of self-injury are more likely to have attempted suicide and report more severe suicidal ideation7, 8, 9. Interestingly, it also applies to substance use disorder, with those who use more substances reporting higher likelihood for suicide9. The number of methods used appears to be a stronger risk factor for suicide than frequency9.
- SEVERITY: The severity of self-injury is also connected with increased risk3, 6.
- AGE OF ONSET: Those who started self-injuring at 12 and younger are more at risk of suicide. The average age of onset for self-injury is 13 to 1610.
- SUICIDAL IDEATION: Suicidal ideation is the strongest predictor of suicide attempt among those who self-injure6, 8.
- NEGATIVE FEELINGS: Teenagers who self-injure and attempted suicide reports more pessimistic perspectives on life, lower self-acceptance, poor family connections, less reason for living and less fear of self-harm than those who self-injured only1, 5.
- INTRAPERSONAL FUNCTION: Those who self-injure for intrapersonal functions (for reasons that relate to themselves, such as emotion regulation or punishment), instead of interpersonal functions (social reasons or a call for help for instance) are more likely to have considered and attempted suicide7, 11.
These elements frequently co-occur. For example, intrapersonal function is usually associated with maintenance of self-injury because the act is effective in regulating emotions11. Similarly, an early age of onset is associated to increased severity10, all of which are risk factors for suicide.
Theories
The Third Variable theory
The Third Variable theory proposes that there is no direct connection between suicide and self-injury, but rather that the link between the two is caused by the sharing of a third variable, such as a psychiatric disorder or psychological distress for instance. But this theory is limited by the fact that people who self-injure remains at increased risk for suicide despite their age, gender or socioeconomic status, or the presence or absence of depression, hopelessness, poor family functioning, history of child abuse, borderline personality disorders or PTSD3.
The Gateway theory
The Gateway Theory speculates that NSSI and suicide are both at the extremities of a self-harm spectrum, and that similar to how cannabis can be a gateway to hard drugs, NSSI can escalate to suicide3.
This theory is supported by the fact non-suicidal self-injury precedes suicidal behaviors as they tend to have different age of onset, with NSSI appearing at a younger age, around 13, whereas suicidal attempts tend to start at 16 years old3. While it shows that self-injury must be taken seriously even if it is not suicidal, NSSI can serve as a warning sign6 and allows about 3 years to offer help and support12.
Joiner’s interpersonal model of suicide
Joiner’s theory is rather similar to the Gateway theory. According to Joiner’s interpersonal model, to die by suicide, someone must both have a desire and acquire the capability for suicide. Acquired capability for suicide means overcoming the fear of pain and death. It is believed that habituation to non-suicidal self-injury might contribute to acquired capability as it diminishes the fear of pain and harm against the self, and reduce sensitivity to pain13, 14. It might explain why those who self-injure more frequently or who use several methods are more at risk of suicide, because as they habituate to self-injury, they need to hurt themselves more frequently or with other methods to experience the same effect. We know for instance that those who self-injure have an increased pain tolerance3 and less fear of suicide6, which appears to support the idea that non-suicidal self-injury decrease the fear of death and pain3.
Unlike the Gateway theory, self-injury only cannot explain suicide in Joiner’s interpersonal model as acquired capability leads to suicide only when it is combined with a desire for suicide. It might explain why the risk for suicide is particularly high when the use of multiple methods of self-injury is combined with a strong risk factor for suicide, such as depression9. Capability can also be acquired through other behaviors than self-injury, such as fighting or extreme sports13. But as we have mentioned above, NSSI in itself has been found to be a risk factor for suicide.
Conclusion
More research is needed to better understand the link between suicide and NSSI. Most studies focus on attempted suicide instead of completed suicide, for ethical and practical reasons. But findings on suicide attempts might not necessarily apply to suicide, as the two behaviors differ. For instance, women are more likely to attempt suicide whereas men are more prone to die by suicide8.
As we have seen, suicidal ideation is the strongest predictor of suicide attempt among those who self-injure. It is therefore important to ask people if they have thoughts about suicide. It is certainly not an easy conversation, but asking about suicide does not put the idea in someone’s mind, and can save lives.
For more information about this topic, I recommend this podcast with Dr. Jennifer Muehlenkamp. She took part in many studies about the connection between NSSI and suicide, several of which has been used to write this article.
References
[1] Whitlock, J., Muehlenkamp, J., Eckenrode, J., Purington, A., Abrams, G. B., Barreira, P., & Kress, V. (2013). Nonsuicidal self-injury as a gateway to suicide in young adults. Journal of Adolescent Health, 52(4), 486-492. https://doi.org/10.1016/j.jadohealth.2012.09.010
[2] Whitlock, J., & Knox, K. L. (2007). The Relationship Between Self-injurious Behavior and Suicide in a Young Adult Population. Arch Pediatr Adolesc Med, 161(7), 634-640. http://dx.doi.org/10.1001/archpedi.161.7.634
[3] Hamza, C. A., Stewart, S. L., & Willoughby, T. (2012). Examining the link between nonsuicidal self-injury and suicidal behavior: a review of the literature and an integrated model. Clinical Psychology Review, 32(6), 482-495. https://doi.org/10.1016/j.cpr.2012.05.003
[4] Nock, M. K., Prinstein, M. J., & Sterba, S. K. (2009). Revealing the form and function of self-injurious thoughts and behaviors: A real-time ecological assessment study among adolescents and young adults. J Abnorm Psychol., 118(4), 816-827. https://doi.org/10.1037%2Fa0016948
[5] Muehlenkamp, J. J., & Gutierrez, P. M. (2007). Risk for Suicide Attempts Among Adolescents Who Engage in Non-Suicidal Self-Injury. Archives of Suicide Research, 11(1), 69-82. https://doi.org/10.1080/13811110600992902
[6] Grandclerc, S., De Labrouhe, D., Spodenkiewicz, M., Lachal, J., & Moro, M.-R. (2016). Relations between Nonsuicidal Self-Injury and Suicidal Behavior in Adolescence: A Systematic Review. PLoS One, 11(4). https://doi.org/10.1371%2Fjournal.pone.0153760
[7] Glenn, C. R., & Klonsky, E. D. (2009). Social context during non-suicidal self-injury indicates suicide risk. Personality and Individual Differences, 46(1), 25-29. https://doi.org/10.1016/j.paid.2008.08.020
[8] Victor, S. E., & Klonsky, E. D. (2014). Correlates of suicide attempts among self-injurers: a meta-analysis. Clinical Psychology Review, 34(4), 282-297. https://doi.org/10.1016/j.cpr.2014.03.005
[9] Turner, B. J., Layden, B. K., Butler, S. M., & Chapman, A. L. (2013). How Often, or How Many Ways: Clarifying the Relationship Between Non-Suicidal Self-Injury and Suicidality. Archives of Suicide Research, 17(4), 397-415. https://doi.org/10.1080/13811118.2013.802660
[10] Muehlenkamp, J. J., Xhunga, N., & Brausch, A. M. (2019). Self-Injury Age of Onset: A Risk Factor for NSSI Severity and Suicidal Behavior. Arch Suicide Res, 23(4), 551-563. https://doi.org/10.1080%2F13811118.2018.1486252
[11] Gardner, K. J., Paul, E., Selby, E. A., Klonsky, E. D., & Mars, B. (2021). Intrapersonal and Interpersonal Functions as Pathways to Future Self-Harm Repetition and Suicide Attempts. Frontiers in Psychology, 12. https://doi.org/10.3389/fpsyg.2021.688472
[12] Westers, N. J., & Muehlenkamp, J. (2021). Nonsuicidal Self-Injury vs. Suicide, with Dr. Jennifer Muehlenkamp [The Psychology of Self-Injury Podcast]. https://the-psychology-of-self-injury.simplecast.com/episodes/nonsuicidal-self-injury-vs-suicide-with-dr-jennifer-muehlenkamp
[13] Joiner, T. (2005). Why People Die by Suicide. Harvard University Press.
[14] Joiner, T. E., Ribeiro, J. D., & Silva, C. (2012). Nonsuicidal Self-Injury, Suicidal Behavior, and Their Co-occurrence as Viewed Through the Lens of the Interpersonal Theory of Suicide. Current Directions in Psychological Science, 21(5), 342-347. https://www.jstor.org/stable/44318606
Exploring self-harm 