Increased Risk for Self-Harm in Autism: Preliminary Findings from the Stockholm Youth Cohort

Background:

Recent evidence suggests that mortality from suicide is increased in autism spectrum disorder (ASD), and particularly in ASD without intellectual disability (ID). Self-harm i.e. self-poisoning or self-injury irrespective of suicidal intent, is the strongest known predictor for subsequent suicide. Self-harm is, however, poorly studied in ASD including whether there are patterns in self-harm methods of prognostic relevance for suicide. In addition, little is known about how co-morbid conditions such as ID and Attention Deficit Hyperactivity Disorder (ADHD) affect risk of self-harm.

Objectives:

To determine the relationship between ASD and self-harm in a large total population study. To investigate risk and protective factors for self-harm in ASD, with emphasis on co-morbid ID and ADHD. 

Methods:

We conducted a total population study using the Stockholm Youth Cohort (N=696,612). Prospectively recorded data for probands followed-up from 0 to a maximum of 27 years by 2011, and their first and second-degree relatives, was collected through record linkage. A total of 11,663 individuals with ASD were identified. Hospital admissions with discharge diagnoses ICD-10 X60-X84 and Y10-Y34 denoted self-harm. We used multivariable Cox proportional hazards regression models to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) of self-harm, overall and categorized as self-harm by poisoning, self-cutting and severe self-harm (including hanging, strangulation, firearm, drowning, jumping from high place/in front of moving objects).

Results:

A diagnosis of ASD was strongly associated with risk of hospital admission for any self-harm

(adjusted HR 4.5, 95% CI 3.8-5.4), self-poisoning (aHR 4.6, 95% CI 3.7-5.6), self-cutting (aHR 5.6 95% CI 3.8-8.3)

and severe self-harm (aHR 5.7, 95% CI 2.5-13.0). This risk increase was even further marked for ASD with co-morbid ADHD for any self-harm (aHR 8.5, 95% CI 7.0- 10.3), self-poisoning (aHR 7.6 95% CI 6.2-9.2), self-cutting (aHR 9.6 95%CI 6.6-13.9) and severe self-harm (aHR 16.1 95% CI 8.6-30.4). In contrast, ASD with ID was not associated with hospital presentations for self-harm.

Conclusions:

These preliminary findings indicate that individuals with ASD have an elevated risk for engaging in self-harm in adolescence and young adulthood, and particularly in severe self-harm. Co-occurring ADHD appears to aggravate this risk, which suggests that identification and treatment of ADHD in ASD may be important for suicide prevention. Co-occurring ID, on the other hand, appears protective. Overall, patients with ASD should be considered a risk group for self-injurious behavior and should be given special attention in clinical settings.