by Michael D. Anestis, M.S.
Suicide is a remarkably troubling phenomenon. If somebody you know has attempted or died by suicide, without question, the topic is a difficult one for you and I suspect you have likely spent a significant amount of time searching for answers to help you better understand what happened. Fortunately, there are many clinical psychologists who devote their professional lives to this same task - understanding and developing effective interventions for suicidal behavior. In several earlier PBB articles, I have described Joiner's (2005) interpersonal-psychological theory of suicidal behavior (IPTS) and outlined the empirical evidence supporting its utility as a way to conceptualize suicide (click on the link to read a sample). Today, I would like to provide a brief description of the theory and to summarize new findings published in the Journal of Abnormal Psychology - the most prestigious psychological journal - by Thomas Joiner, Kim Van Orden, Tracy Witte, Eddie Selby, Jessica Ribeiro, Robyn Lewis, and David Rudd.
The IPTS posits that there are three jointly necessary variables that must be present in order for an individual to die by suicide or to make a serious attempt: perceived burdensomeness, thwarted belongingness, and the acquired capability for suicide. Perceived burdensomeness represents a belief on the part of an individual that he or she does not make any notable contributions to the world and, in fact, serves as a liability to others. Thwarted belongingness represents a belief on the part of an individual that he or she does not have meaningful relationships with others, either because others do not care or because, while they do care, they can not relate to the individual's experiences and, as such, remain at a distance. These two variables - perceived burdensomeness and thwarted belongingness - combine to represent the desire for suicide and help to identify who wants to die by suicide. The third variable - the acquired capability for suicide - represents habituation to physiological pain and fearsome experiences due to repeated exposure to painful and provocative events. This variable is distinct from suicidal desire and helps identify who can die by suicide. In summary, the theory distinguishes between suicidal thoughts and behaviors and posits that desiring suicide does not mean an individual can enact lethal self-harm and, alternatively, high levels of the acquired capability do not mean an individual wants to attempt suicide.
I realize that this theory may be very different from the ways in which you think of suicide and I again encourage you to read our earlier articles on the IPTS in order to gain a better understanding of the evidence supporting its validity. For now, however, I would like to turn my attention to the studies conducted by Joiner and colleagues (2009) published in the current issue of the Journal of Abnormal Psychology. This particular paper featured results from two separate studies.
In the first study, the authors wanted to examine whether perceived burdensomeness would interact with thwarted belongingness to predict suicidal ideation above and beyond the effects of recent and lifetime depressive symptoms. 1,763 individuals between the ages of 19 and 26 took part in structured diagnostic interviews and filled out a series of questionnaires. 815 of those individuals endorsed either the depressed mood or anhedonia symptom of major depression and were included in the analyses. Importantly, the measures used in this particular study were not specifically designed to measure the components of the IPTS. Such measures exist, but were not available when this dataset was developed. Instead, a measure of "general mattering" was used to represent perceived burdensomeness and a measure of family social support was used to represent thwarted belongingness.
The results of this first study were quite compelling. The interaction of perceived burdensomeness and thwarted belongingness did, in fact, predict suicidal ideation, even when controlling for recent and lifetime symptoms of depression. What this means is that, while depressive symptoms can help us predict who is vulnerable to having thoughts of suicide, perceived burdensomeness and thwarted belongingness provide significantly more information and serve as stronger predictors of suicidal ideation. Importantly, when the authors examined the nature of the interaction, they found that individuals with high levels of both perceived burdensomeness and thwarted belongingness were at the greatest risk of experiencing prominent thoughts of suicide. An interaction between the two variables means that, when both variables are present, the results is more than the sum of its parts.
In the second study, Joiner and colleagues (2009) wanted to examine the main hypothesis of the theory: that all three variables would interact to predict suicidal behavior, again controlling for depressive symptoms as well as a number of other important variables. The sample consisted of 313 individuals who had been referred to treatment due to severe suicidality, defined as either a recent attempt or ideation severe enough to warrant evaluation for hospitalization. Here again, the authors did not have access to theory specific measures, so they utilized measures of similar constructs in an effort to examine the IPTS components. Perceived burdensomeness and thwarted belongingness were assessed using items from the Suicide Probability Scale (SPS; Cull & Gill, 1988). The acquired capability was measured by evaluating participants' lifetime number of suicide attempts.
The results of study 2 were equally compelling. The three-way interaction of perceived burdensomeness, thwarted belongingness, and the acquired capability for suicide predicted whether or not a participant's recent suicidal crisis involved an actual suicide attempt (as opposed to only suicidal ideation), even when controlling for age, biological sex, marital status, ethnicity, family history of suicide, family history of depression, family history of bipolar disorder, current and past diagnoses of depression and bipolar disorder, current depressive symptoms, hopelessness, and featured of borderline personality disorder. In other words, even when we factor in the impact of all of those other variables, the three-way interaction of the IPTS components provided significantly greater predictive utility with respect to participants' recent suicidal behavior. Importantly, when the authors examined this interaction, they found that individuals with high levels of all three theory components were at the greatest risk for having actually attempted suicide in their most recent suicidal crisis.
As you read over these results, I suspect you may have wondered why the authors used such complicated analyses and distinguished between suicidal desire and behavior. There are several reasons for this. First of all, while suicidal ideation is certainly dangerous, it is far more common than is suicidal behavior. As such, it is vital that we understand what distinguishes those who merely think about the behavior and those who actually attempt. Additionally, for every completed suicide, there are 25 additional attempts. As such, we need to understand what distinguishes those who die by suicide from those who make non-lethal attempts. Additionally, while diagnoses such as depression, bipolar disorder, and borderline personality disorder are all certainly associated with highly elevated suicide rates, most individuals with these diagnoses do not die by suicide, so we need to understand what causes some such individuals to be at greater risk. The IPTS does this by considering several variables at the same time and, unlike prior theories, the IPTS takes into account the cumulative effect of exposure to physical pain and the threat of death. This particular study, without question, had some limitations. At the same time, this is true of any study in any field and other data utilizing theory specific measures has since been acquired and will soon be discussed here on PBB. In fact, the September 2009 PBB featured article, written by Chad Morrow of the United States Air Force, will cover data examining the utility of the IPTS in understanding suicidal behavior in the military and will be published on the site on September 1.
In the meantime, I look forward to hearing your thoughts on the IPTS in general and these studies in particular. If you or somebody you know is currently experiencing thoughts of suicide, please call 1-800-273-TALK or dial 911 for immediate help. If you would like to learn more about the IPTS, we recommend the following resources, all of which are available through our online store:
Why People Die by Suicide
The Interpersonal Theory of Suicide: Guidance for Working With Suicidal Clients
Mike Anestis is a doctoral candidate in the clinical psychology department at Florida State University.
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