Dispelling Despair
Authors:   , Huntjens Anne 
Published: November 2024

Suicidal behaviour among autistic individuals has gained increasing recognition in recent years, yet research on effective interventions for addressing suicidal ideation (SI) and suicide attempts (SA) remains limited. This thesis investigates the prevalence of suicidal behaviour in autism, the effectiveness of Dialectical Behavior Therapy (DBT) in addressing these behaviours, its impact on secondary outcomes, cost-effectiveness, and the mediating role of emotion regulation.
Chapter 2 presents a meta-analysis exploring the prevalence of suicidal behaviour in autism. This analysis, involving 52 studies and 88,509 autistic individuals, reveals alarmingly high rates of lifetime suicidal ideation (37.2%) and suicide attempts (15.3%). For 12-month prevalence, these rates were 25.4% and 14.1%, respectively. Subgroup analyses uncover variations based on age, geographic region, data collection methods, and sample characteristics. The findings emphasise challenges posed by inconsistent methodologies, underscoring the need for validated suicidality assessment tools and improved diagnostic approaches in future research.
The study protocol for evaluating DBT’s effectiveness is detailed in Chapter 3. Conducted as a single-blind, multisite, randomised controlled trial (RCT) across six Dutch mental health centres, the study includes 123 autistic adults exhibiting suicidal behaviour. Participants were randomised to either DBT or treatment as usual (TAU), with the primary outcomes being the severity of suicidal ideation and the frequency of suicide attempts, while secondary outcomes included depression severity and social anxiety.
Chapter 4 presents the clinical trial findings. DBT significantly reduces both suicidal ideation and suicide attempts compared to TAU at the six-month treatment endpoint. Although these reductions persist, the statistical significance diminishes at the 12-month follow-up due to TAU outcomes converging with DBT results. Depression severity decreases significantly with DBT, with sustained improvements at follow-up, while the effect on social anxiety remains limited. Importantly, DBT is associated with fewer adverse events, with no suicides reported in the DBT group compared to two in the TAU group, reinforcing its safety and acceptability.
The broader impacts of the intervention on social functioning and autism-related traits are examined in Chapter 5. DBT enhances social functioning and quality of life significantly more than TAU, with these improvements maintained at follow-up. Autism-related traits decrease in both groups over time, with the DBT group showing a more pronounced reduction. These findings demonstrate DBT’s clinical relevance not only for suicidality but also for broader functional and psychosocial outcomes in autism.
Cost-effectiveness analyses are presented in Chapter 6, where DBT emerges as a dominant option from both healthcare and societal perspectives. The intervention reduces overall costs compared to TAU, leading to fewer hospitalisations and greater quality-adjusted life years (QALYs). These results highlight DBT’s economic viability and its potential for integration into routine care.
The mechanisms underlying DBT’s effectiveness are explored in Chapter 7, focusing on the role of emotion regulation (ER). Structural equation modelling reveals that ER mediates 67% of DBT’s treatment effect on suicidal ideation. A sequential model addressing specific ER factors in order—to reduce suicide risk, enhance emotional awareness, consolidate skills, and align coping strategies with long-term goals—produces stronger outcomes. These findings underscore the importance of structured, targeted approaches to optimise DBT’s therapeutic effects.

In conclusion, this thesis establishes DBT as a promising, safe, and cost-effective intervention for reducing suicidal behaviour in autistic individuals. The findings highlight DBT’s benefits for both suicidality and broader psychosocial outcomes while demonstrating its economic advantages. Nevertheless, replication of these findings in further high-quality RCTs is essential to validate results and advance evidence-based care for autistic individuals with suicidality. This research emphasises the urgent need for tailored interventions and methodological refinement to enhance therapeutic outcomes for this high-risk population.