Paper: "Potential mechanisms underlying suicidality
in autistic people with ADHD: testing hypotheses
from the interpersonal theory of suicide"
This paper was published in 2023, in the journal Autism in Adulthood.
You can click HERE to download a PDF of the paper. (Note for copyright purposes, it is the accepted manuscript, not the final published version).
This study follows on from a previous study on the same topic. You may like to read that one first (it will open in a new tab). When you are ready, see below for a plain English summary and explanatory videos.
Why is this an important issue?
Suicide is a leading cause of premature death in autistic people, but not everyone is equally at risk. Understanding the psychological processes which underlie suicidal thoughts and actions may help us identify who is in greatest need of support, how to best support them, and how to change society so that fewer autistic people end up at that crisis point.
Within the autistic community, emerging research suggests that autistic people with ADHD have an especially difficult time throughout their lives. Living as an autistic person, or as a non-autistic person with ADHD (an “ADHDer”), is hard enough: both autistic people and ADHDers are stigmatised neuro-minorities. Autistic people with ADHD (“autistic ADHDers”) are a double minority, and there are few adaptations designed for them.
Compared with neurotypical children and autistic children without ADHD, autistic ADHDers are more likely to struggle academically at school, more likely to be isolated and possibly bullied; unsurprisingly, they’re also more likely to have poor mental health. As adults, in comparison with autistic people without ADHD, autistic ADHDers have greater difficulty obtaining and maintaining employment, and are less likely to report having supportive friendships.
There is some early evidence that autistic ADHDers are at higher risk of suicide than people with a single form of neurodivergence (i.e. autistic people without ADHD, ADHDers who aren’t autistic). We wanted to see if this is indeed the case, and if so, whether higher risk in autistic ADHDers can be explained by psychological theories about suicide.
Here is a video summary of the study. You can toggle your view by clicking the icon in the top right corner, and turn captions on and off by clicking the 'CC' button.
What was the purpose of this study, and what did the researchers do?
We investigated whether autistic ADHDers are more vulnerable to suicidality by looking at self-reported suicidal thoughts and behaviour in autistic people with and without ADHD. In addition, we examined two explanations for possibly higher suicide risk in autistic ADHDers. These two theoretical pathways, or hypotheses, were based the interpersonal theory of suicide.
What were the results of the study?
Autistic participants with likely ADHD did indeed have poorer mental health: they had higher anxiety and depression, and were more likely to report feeling like a burden. Because of these higher rates of depression and perceived burdensomeness, “likely ADHD” in autistic participants was indeed associated with higher rates of suicidal thoughts in the past year. The higher rates of perceived burdensomeness experienced by autistic participants with likely ADHD, furthermore, were linked with more numerous suicide attempts in these participants. These relationships might be depicted as follows:
These findings partly support hypothesis 1: that higher rates of perceived burdensomeness in autistic ADHDers would be associated with higher rates of suicidality. Autistic people with likely ADHD did not have stronger feelings of thwarted belongingness. In contrast to the suggestions of the interpersonal theory of suicide, we didn’t find a relationship between higher levels of thwarted belongingness and suicidality in autistic people, anyway. (That was the topic of another paper with the same sample - click here to read it in a separate window).
What about hypothesis 2?
We did indeed find that the more hyperactive/impulsive features a person had, the greater their exposure to painful, traumatic and/or thrill-seeking events. Because of this, people with higher hyperactive/impulsive features had higher scores in acquired capability for suicide, and because of their higher capability for suicide, they tended to report more numerous suicide attempts.
Capability for suicide is about how afraid you are of pain and death, and your levels of pain tolerance. Exposure to painful, traumatic and/or thrill-seeking events was indeed associated with ‘acquiring’ capability for suicide (i.e. developing tolerance for pain, becoming less frightened of pain and death), but our data also showed that exposure to these kind of events was associated with higher risk of suicide attempts all by itself, regardless of the effect of these events on suicide capability.
This finding means that there are at least two ways that experiencing these kind of events affects a person's risk of suicide, with one of these ways being that these events result in 'acquiring' suicide capability. It makes sense that painful or traumatic events can have many psychological impacts other than just their effect on suicide capability. For instance, experiencing these kind of events may be associated with developing PTSD or complex PTSD, depression and other mental illnesses, and these mental illnesses may increase suicide risk.
You could depict this pattern of relationships as follows:
Autistic people tell us that trauma, PTSD and complex PTSD are major factors in their suicide rates. This study supports that in highlighting relationships between traumatic events and suicidality. Unfortunately the measure we used couldn’t separate out events that were physically painful, emotionally traumatic or thrill-seeking, or identify exactly which ones were associated with suicide risk.
What are potential weaknesses in the study?
Because this study looked at a snapshot of participants’ current states, we cannot ascertain the direction of relationships between variables. For example, it might be that experiences of suicide cause feelings of burdensomeness after the fact, rather than this factor contributing to suicide.
We used a rating scale to identify “likely ADHD” in our participants. We did this because we know that many autistic people will have undiagnosed ADHD, and many ADHDers will have undiagnosed autism! But it means that we can’t be 100% sure that we are comparing autistic people with and without ADHD.
We did not pay a lot of attention to inattentive features of ADHD. Research in ADHDers suggests that inattentive features can be associated with a number of difficulties in the world. Incidentally, inattentive features of ADHD are more commonly seen in women, and people with inattentive features are much more likely to be overlooked for diagnosis. As such, it seems likely that inattentive features might also have repercussions on a person’s life that affects their suicide risk, but this is an important question for future research.
There are a number of theories which highlight different risk factors for suicide, but we looked only at those proposed by the interpersonal theory of suicide. Furthermore, we used questionnaires which hadn’t been developed with autistic people in mind, unfortunately because there weren’t any available at the time.
Finally, the sample was not representative of the whole autistic population: most notably, people of colour, non-binary and transgender autistic people were not adequately represented. Neither were autistic people with intellectual disabilities that would have prevented them from taking part.
Thank you for reading!
How will these findings help autistic adults now or in the future?
Very little is known about whether autistic ADHDers might be at even higher risk of suicide than people with either ADHD or autism alone, and why this might be the case.
These findings indicate feelings and experiences which are relevant to suicide risk in autistic people and autistic ADHDers, which might thus be important to target in interventions. Feelings of burdensomeness, for instance, were associated with suicidal thoughts and with suicide attempts. Autistic people with “likely ADHD” had poorer mental health in general, with greater rates of anxiety, depression and feelings of burdensomeness. Because of their higher rates of depression and perceived burdensomeness, they had higher rates of suicidality.
Since the findings highlight that feeling like a burden is very toxic to autistic people, they highlight a need for policy-makers, practitioners and wider society to consider how and where those feelings emerge. Theories of suicidality often focus on the person and their thoughts and feelings, but we emphasise that a person’s thoughts and feelings come from their experiences in the world. If autistic people feel a sense of being a burden, it is crucial to search for the sources of those feelings and try to prevent them arising.
The findings also corroborate what autistic people have told us about the importance of traumatic events for suicidality. Our findings suggest that one way that traumatic events may affect suicide risk is through affecting capability for suicide: i.e. people becoming less frightened of pain and death, and having greater tolerance for pain.
However, the data also suggest that experiencing traumatic events affected suicide risk in other ways; speculatively, perhaps through the development of PTSD, complex PTSD, and other post-trauma symptoms. These findings highlight that exposure to traumatic life events must be taken seriously in autistic people.
Hypothesis 1: Given that they often struggle more in the world than do people with a single form of neurodivergence, autistic ADHDers might be more vulnerable to feelings of thwarted belongingness (a state of social alienation and aloneness) and perceived burdensomeness (the feeling that one is a liability or burden to others). The interpersonal theory of suicide suggests that feelings of thwarted belongingness and perceived burdensomeness are preceding risk factors for suicide ideation (the desire to end your own life) - so if autistic ADHDers are more likely to feel this way, it makes sense that they would have higher rates of suicidality.
Hypothesis 2: Hyperactive/impulsive features associated with ADHD might mean individuals are more likely to be exposed to painful or traumatic events. Like autistic people, ADHDers are more vulnerable than the general population to dangerous and traumatic events: they are more likely to be victimised, assaulted or caught up in accidents. However, people with hyperactive/impulsive features are also drawn to a range of thrill-seeking, adrenaline-boosting kind of activities which hold potential danger: for instance, extreme sports, motorbiking, skydiving and so forth.
The interpersonal theory of suicide suggests that people who are exposed to painful or traumatic events, or even thrill-seeking but dangerous kinds of activities, will acquire ‘capability’ for suicide. This means they will develop higher tolerance for pain, and be less frightened of pain and death.
Developing ‘capability’ for suicide increases someone’s risk of attempting or dying by suicide as it means that should they want to end their own life, they are able to overcome strong, evolutionary instincts to avoid pain and keep ourselves alive. Self-injury is another means through which people can acquire capability for suicide, as investigated in another one of our studies (link will open in new window).
To test these two pathways that might explain higher suicide risk in autistic ADHDers, we asked 314 autistic adults to complete an online survey including measures of thwarted belongingness and perceived burdensomeness, as well as their exposure to painful, traumatic and thrill-seeking events, and their levels of acquired capability for suicide.
Our autistic sample were nearly all diagnosed as adults. Although 54 reported that they’d received a formal diagnosis of ADHD, we suspected that a much higher number might have undiagnosed ADHD. We believed this because up until recently (2013), a person couldn’t be officially diagnosed with autism and ADHD together, while we now know that perhaps 40% of autistic people also have ADHD.
To find autistic participants who might have undiagnosed ADHD, we used a popular measure of ADHD, the Connor Adult ADHD Rating Scale. It turned out that 142 of our autistic participants (45%) had scores higher than the cut-off indicative of likely ADHD. We therefore compared suicidal experiences between autistic participants above the ADHD cut-off (since we could not formally diagnose them, we describe these individuals as having “likely ADHD”), and those below the cut-off (individuals unlikely to have ADHD).
If you found this interesting, you may like to read:
If you are struggling with feeling suicidal, I am deeply sorry. Please, please look at the resources page, just in case there is anything helpful for you