Background: Autistic individuals frequently experience psychiatric co-occurring conditions, but the association with self-harm/suicidality according to these conditions was not yet elucidated. We aimed to summarize the association between self-harm/suicidality and psychiatric co-occurring conditions in autistic people.

Methods: We systematically searched PubMed, Scopus, Embase, Web of Science, and Cochrane Database of Systematic Reviews until June 4, 2024 (PROSPERO registration number: CRD42023412860). Observational studies were included that provided information to calculate the odds ratio (OR) regarding the association between self-harm/suicidality and psychiatric co-occurring conditions in autistic individuals. We summarized the identified associations by presenting OR range or meta-analyzing when 7 or more estimates are available.

Findings: The systematic search found 20 eligible studies with 301,841 participants. Our findings suggested that autistic individuals with any psychiatric disorder (k = 1; OR 3.55; 95% CI 1.27-9.98), ADHD (k = 3; OR range: 1.07-1.65), or mood disorder (k = 1; OR 1.26; 95% CI 1.05-1.51) may be associated with higher odds of self-harm than those without these conditions. We identified potential positive associations between suicidality and the following co-occurring conditions: any psychiatric disorder (k = 1; OR 11.65; 95% CI 10.68-12.71), psychotic disorder (k = 4; OR range: 1.95-10.97), mood disorder (k = 3; OR range: 1.75-9.82), bipolar disorder (k = 2; OR range: 2.55-4.95), depressive disorder (k = 10; pooled OR 2.29; 95% CI 1.39-3.77), trauma- and stress-related disorder (k = 2; OR range: 1.28-10.47), and adjustment disorder (k = 1; OR 3.52; 95% CI 2.89-4.28).

Interpretation: We found psychiatric co-occurring conditions that may be associated with higher odds of self-harm/suicidality in autistic individuals. However, our findings should be interpreted with caution considering the limited number of included studies. We suggested that clinicians should remain vigilant for autistic individuals with psychiatric co-occurring conditions for their potentially higher likelihood of self-harm and suicidality.

Funding: This research was supported by a grant of the R&D project, funded by the National Center for Mental Health (grant number: MHER22A01).

The authors have no competing interests to declare relevant to any content of this manuscript.