(This is the first post in this series; my second post talks about what suicide prevention means in practice. My third post discusses some assumptions made by suicide prevention initiatives)

September 10^th is World Suicide Prevention Day, a day of awareness held by the International Association of Suicide Prevention (IASP) alongside the World Federation for Mental Health and the World Health Organisation.

After reading about the day and the organisations involved, I was curious about how suicide is understood from a research perspective, and what explanations or theories about suicide are used to talk about suicide prevention. This post covers a widely-used theoretical approach – the Interpersonal-Psychological theory of suicide. The interpersonal-psychological theory (IPT for short) was first created by Joiner (2005), and is the theory used to guide the IASP.

In the IPT, two factors lead to suicidal behaviour. Firstly, a person must have the desire to die, which is linked to two feelings. One feeling is perceived burdensomeness – a person’s belief that they are a burden on the people they care about, or that their loved ones would be made better off by their death. The other feeling is thwarted belongingness – a person’s sense of alienation from the social circles and people they care about.

Each feeling make people more likely to desire to die, according to the IPT, while experiencing both together is associated with the greatest risk. However, experiencing that desire does not equate to acting on it; the number of people who experience suicidal thoughts is far larger than the number who ever attempt suicide. In the IPT, a second factor is required – people must acquire the ability to act on their desire.

Ability in this sense doesn’t refer to the physical ability to carry out suicidal acts. It instead means a person’s emotional/cognitive ability to bypass their usual fear of death and pain, to inflict violence on themselves. Joiner named it acquired capability. In the IPT, this ability is acquired through past trauma or pain which results in higher pain tolerance and weakened responses to self-preservation instincts. This is thought to be a linear relationship, where experiencing a greater cumulative number or severity of painful experiences directly leads to a greater pain tolerance and a decreased fear of death. In this context, past painful experiences can come from a variety of sources beyond trauma. The IPT suggests that people who self-injure may be more likely to attempt suicide due to previous experience of bypassing their self-preservation instincts to cause themselves pain. Similarly, people who often witness other people’s traumatic and painful events would also acquire that tolerance.

Conclusion

Looking at the IPT, it’s fairly easy to understand how this theory has become dominant in research on suicide.

Its component parts have high face validity and seem to be logical pieces of the puzzle. People’s feelings of thwarted belongingness and perceived burdensomeness can both be researched to an extent, and do appear to be connected to people’s likelihood of attempting suicide.  Finally, Joiner’s concept of acquired ability offers an explanation of why comparatively few people complete suicide compared to the amount of people who experience suicidal thoughts during their lives.

However,  acquired capability is difficult to demonstrate or study due to how broad the concept is. While research does show that traumatic events are connected to suicide, this can’t fully cover the emotional/ cognitive quality of Joiner’s acquired capability. Similarly, testing his linear approach, and the idea of cumulative severity, seems like it would require the ability to rank or order trauma-causing events. To me, this idea sounds impossible to carry out at any scale beyond a single person.