Content warning: suicide, obviously

Hdley and Uljarević 2018, Systematic Review of Suicide in Autism Spectrum Disorder: Current Trends and Implications, Current Developmental Disorders Reports, link

“There is increasingly strong evidence that suicide is a critical issue facing people with ASD—recent studies report increased suicidal thoughts, behavior, and premature death by suicide compared to both general and clinical populations.”
“Prevalence of suicide ideation ranged from 11 to 66% and suicidal attempts from 1 to 35%.”
“Hirvikoski et al. reported a mortality rate for premature death by suicide in people with ASD of 0.31%, which compared to 0.04% in gender and age matched general population controls; odds ratio [OR] = 7.55 [6.04, 9.44], p = not reported.”
“To date, studies have yet to unravel the underlying causal mechanisms leading to heightened risk of death by suicide in the ASD population.”

Hedley et al 2018, Risk and protective factors underlying depression and suicidal ideation in Autism Spectrum Disorder, Depression and Anxiety, link

“Participants were 195 (94 females) individuals with ASD aged 14–80 years (Mage = 36.69, SD = 15.57 years) who were recruited from a range of sources, including support groups, schools, universities, and advertisements through relevant website and social media. […] Participants were recruited through the nationwide Australian Longitudinal Study of Adults with Autism (ALSAA; target age range 25 years and older) and the Longitudinal Study of Australian School Leavers with Autism (SASLA; target age range 15–25 years).”
“Regression analyses revealed that loneliness, satisfaction with social support, and ASD traits predicted depression scores. Satisfaction with social support predicted suicidal ideation, however, it was no longer a significant predictor after the effects of depression were taken into account. Path analysis showed that ASD trait severity was independently related to depression, that the effect of number of social supports on depression was mediated by loneliness and satisfaction with social support, and that effects of loneliness and satisfaction with social support on suicidal ideation were mediated by depression.”
“Correlational analysis showed that lower levels of social support, both in terms of the number of social supports and satisfaction with available social support, and higher loneliness, were associated with depression and suicidal ideation.”
“Path analysis revealed a number of important findings. First, ASD trait severity independently predicted depression, even after controlling for the effects of satisfaction with social support and loneliness. However, ASD trait severity was not significantly correlated with suicidal ideation.”
“This study supports a model whereby loneliness and social support operate respectively as protective and risk factors for depression and suicidal ideation in ASD.”
“Thus, it may be beneficial for interventions to assist individuals to identify and increase the availability of quality social support networks, and to provide opportunity for regular social interaction, to minimize potentially harmful effects of social isolation.”

Casten et al 2023, The combination of autism and exceptional cognitive ability is associated with suicidal ideation, Neurobiology of Learning and Memory, link

“Autism with co-occurring exceptional cognitive ability is often accompanied by severe internalizing symptoms and feelings of inadequacy.”
In the first sample (N = 1,074 individuals seen at a clinic specializing in gifted/talented youth), we observed a striking excess of parent-reported suicidal ideation in autistic individuals with IQ 120 (Odds Ratio = 5.9, p = 0.0007). In a separate sample of SPARK participants, we confirmed higher rates of suicidal thoughts compared to non-autistic children from the ABCD cohort (combined N = 16,049, Odds Ratio = 6.8, p < 2.2e-16), and further that autistic children with suicidal thoughts had significantly higher cognitive ability (p < 2.2e-16) than those without.
Clinical sample: “Over a ten-year period (2009-2019), data from 1,254 evaluations from a university-based clinic that specializes in the assessment and counseling of gifted and twice-exceptional students were recorded.” apparently close to the University of Iowa; SPARK cohort: “SPARK is an autism study of nearly 300,000 individuals in the United States. […] There was complete CBCL data available for 6,766 children in SPARK, 4,171 of which were between the ages of 8 to 15 (subset used for comparison to ABCD cohort), and 1,982 had quality control passing genotype and behaviorally-predicted IQ data.”; ABCD cohort: “The ABCD cohort [14] is a typically-developing cohort, which was recruited regardless of neuropsychiatric conditions, meant to represent a more general population sample than case/control cohorts. Release 3 data were used, CBCL data was available on 11,878 children. Z-scaled NIH toolbox full composite scores were the proxy used for IQ in this cohort, and these scores were available for 4,999 children.”
“Twice-exceptional children, i.e., those with autism and at least one IQ subscale score ≥ the 90th percentile, showed the highest rate of suicidal thoughts, at 12.9%, compared to only 2.4% in IQ matched controls”
“The main contribution of this study is in drawing attention to the significantly increased risk of suicidal ideation faced by members of a ”double minority” defined by exceptional cognitive ability and autism. Our analyses demonstrate that increasing IQ switches from a protective factor in non-autistic individuals to a risk factor for suicidal ideation in autistic youth.”
“With multiple large cohorts and through a series of complementary analyses, we repeatedly demonstrated a robust link between higher cognitive ability and signs of suicidal ideation, specifically in an autistic context. There is evidence that this is at least partly genetic in nature: polygenic scores for cognitive performance and educational attainment were positively associated with thoughts of suicide in autistic youth and their parents, respectively.”

Bentum et al 2024, Occurrence and predictors of lifetime suicidality and suicidal ideation in autistic adults, Autism, link

“This study examined the occurrence of various potential risk factors for lifetime suicidal behavior and suicidal thoughts in the past month in a Dutch cohort (Netherlands Autism Register) of autistic individuals using the Suicidal Behaviors Questionnaire (SBQ-R) and the Suicidal Ideation Attributes Scale (SIDAS).”
“In the final sample (n=421), backward linear regression analyses identified the following predictors for suicidal behavior: psychiatric comorbidity, loneliness, and higher number of autistic traits, F(3, 240)=21.22, p<0.001, with R2 of 0.21. For suicidal thoughts in the past month, psychiatric comorbidity and a higher number of autistic traits were significant predictors, F(2, 241)=20.34, p<0.001, with R2 of 0.14.”
“Loneliness predicted lifetime suicidal behavior scores but not suicidal thoughts in the past month. This is consistent with findings that loneliness was more strongly associated with suicidal behavior in the longer term than in the short term (McClelland et al., 2020). Autism-related traits may enhance the potential for feeling lonely if mutual difficulties in social communication and understanding, and social interactions between autistic people and neurotypical people are experienced repeatedly over a long period. This is in line with the double empathy problem […]”
“One suggestion might be to target feelings of thwarted belongingness, as it is hypothesized to be dynamic and amenable to therapeutic change (van Orden et al., 2010). Loneliness should be one of the main factors in treatment to reduce suicidal risk.”