AbstractObjectiveSelf‐harm among young autistic individuals is a clinical challenge, and the risk of premature death by suicide is strongly increased in this group. Using the advantage of total‐population and family‐based data, we investigated whether autism per se is a risk factor for self‐harm independently of psychiatric comorbidities and how it differs from self‐harm in non‐autistic individuals.MethodsWe used The Stockholm Youth Cohort, a total‐population register study, including all residents in Stockholm County aged 0–17 years between 2001 and 2011.Study participants were followed from age 10 to 27 for hospital admissions because of self‐harm. We used modified Poisson regression to calculate relative risks (RR) using robust standard error to derive 95% confidence intervals (CI).ResultsIn all, 410,732 individuals were included in the cohort (9,070 with a diagnosis of autism). Autistic individuals had a fivefold increased adjusted relative risk of self‐harm (RR 5.0 [95% CI 4.4–5.6]). The risk increase was more pronounced for autism without intellectual disability and particularly high for self‐cutting 10.2 [7.1–14.7] and more violent methods 8.9 [5.2–15.4]. The association between autism and self‐harm was independent of, but clearly exacerbated by comorbid psychiatric conditions. It was of similar magnitude as risks linked to these conditions per se, and not explained by shared familial factors.ConclusionSelf‐harm severe enough to present to medical services is as common in autistic youth as in those with depression or ADHD. Potentially more lethal methods are more likely to be used of autistic self‐harmers.