Siblings of Autistic Children Face Elevated Mental Health Risks in Landmark Cohort

Siblings of autistic children carry a substantially higher risk of being diagnosed with mental disorders, being prescribed psychotropic medications, and showing reduced early school engagement, according to one of the largest population-based studies of these families ever conducted. The research, published in Child Psychiatry & Human Development, drew on linked administrative health, prescription and education records for the entire Canadian province of Manitoba and followed siblings for up to 24 years.

The research team, led by Cara Katz of the University of Manitoba, constructed three mutually exclusive longitudinal cohorts from the Manitoba Centre for Health Policy repository, which captures population-level health and social data for the whole province. Probands were children under 18 diagnosed with autism spectrum disorder, Down Syndrome, or no neurodevelopmental disorder between 1995 and 2009, a window chosen to allow for a minimum of 10 and a maximum of 24 years of follow-up. Siblings were identified in the data using de-identified personal health information numbers linked to an individual parent, all siblings were included where multiple siblings existed, and the cohorts were not restricted to singleton births. The final sample comprised 5,409 siblings of autistic probands, 3,952 siblings of Down Syndrome probands, and 328,015 siblings of neurotypical probands.

The investigators reported using stabilized inverse probability treatment weighting in all regression models to reduce bias between cohorts, with weighting criteria including sex, birth year within one year, family income quintile and urban or rural region. Given the sample size discrepancies between the groups, siblings of neurotypical probands were matched on birth year, sex and region in a five-to-one ratio. Regression models, selected according to the type of study outcome, produced adjusted relative risks and rates, with adjustment for family size, birth order, sibling age at proband diagnosis, sibling mental and neurodevelopmental disorders other than the disorder of interest, parent mental disorders and parent physical comorbidity, alongside demographics. In the autism versus Down Syndrome comparison, sibling seizure disorder and intellectual disability were included as proxies of autism severity.

The headline mental health findings were stark. Compared with siblings of neurotypical probands, siblings of autistic probands showed elevated adjusted risk of every mental disorder examined except substance use disorder, with all comparisons statistically significant at p < 0.001. This included a 53 percent increased risk of hospitalized suicide attempts, a link the authors believe had not previously been established using population-based data. Prior meta-analytic work had reported greater internalizing and externalizing difficulties in this group, and earlier registry studies found increased psychiatric and neurodevelopmental diagnoses even after adjusting for maternal socioeconomic status, occupation, parental psychiatric history and parental age, but the present study extends those results with a broader outcome set and more complete covariate adjustment.

The Down Syndrome comparison revealed a more nuanced picture. Siblings of autistic probands were at higher adjusted risk than siblings of Down Syndrome probands of mood and anxiety disorders (adjusted relative risk 1.18, 95 percent confidence interval 1.12 to 1.24), disruptive and impulse control disorders (aRR 1.50, CI 1.34 to 1.67) and other neurodevelopmental disorders (aRR 1.43, CI 1.33 to 1.53). Yet they were at lower risk of substance use disorder (aRR 0.82, CI 0.75 to 0.90), and there was no difference between the two groups in suicide attempts. Because families of autistic children and children with Down Syndrome both report elevated parental stress and service barriers, this comparator helps separate the psychosocial strain of living with a disabled sibling from autism-specific genetic recurrence risk, which is substantially higher for autism than for Down Syndrome.

A surprising set of findings emerged for the Down Syndrome siblings themselves. Relative to neurotypical siblings, they showed elevated risk of bipolar disorder (aRR 1.32, CI 1.21 to 1.43), psychotic disorder (aRR 1.47, CI 1.31 to 1.65) and substance use disorder (aRR 1.12, CI 1.04 to 1.21), alongside reduced neurodevelopmental disorder risk (aRR 0.71, CI 0.67 to 0.76). They also faced higher risks of hospitalization and unintentional injury, lower odds of passing Grade 12 provincial exams in mathematics and language arts, and reduced likelihood of graduating high school on time. The authors suggest this may reflect a unique genetic risk profile and note that the difficulties of siblings of people with Down Syndrome warrant future study in their own right.

Psychotropic prescribing told a consistent story. Using linked prescription records, the study found, for the first time, that siblings of autistic probands were more likely than either comparison group to be prescribed antidepressants, sedatives, mood stabilizers, ADHD medications and antipsychotics, with all comparisons significant at p < 0.001. The authors interpret this partly as a consequence of the elevated diagnostic burden, but also flag the possibility of increased case-finding within these families or a tendency to prioritize pharmacologic over non-pharmacologic treatments. On the physical health side, siblings of autistic probands actually fared better than Down Syndrome siblings, with lower risks of hospitalization (aRR 0.78), unintentional injury (aRR 0.88) and death (aRR 0.50), and they showed no elevated physical health burden relative to neurotypical siblings, a result that contrasts with smaller earlier studies reporting increased atopic disease in this group.

The educational results, which the authors explicitly label exploratory due to limitations in the administrative education data, were mixed. Early developmental indices measuring social, physical and overall readiness differed between siblings of autistic and neurotypical probands, and siblings of autistic probands were less likely to have established school engagement competency than either comparison group. However, there were no differences in later academic competencies, no group differences in school enrolment after adjustment, and no differences on communication indices, a pattern the authors suggest may indicate effective early recognition and intervention within schools. This partially contradicts previous literature reporting broadly lower academic achievement among siblings of autistic children, possibly reflecting methodological differences between studies.

The authors are careful about interpretation. Administrative data capture treatment-seeking populations, and physician-based diagnoses likely miss subclinical conditions, including subthreshold expressions of the broader autism phenotype that cannot be readily identified in claims records. Systemic barriers to service access may lower diagnostic coverage in rural areas, which the team partially mitigated by controlling for rural versus urban residence. Sibling linkages relied on a single parent, usually the mother, potentially missing siblings in blended families, and probands identified as having global developmental delay, who made up 8.3 percent of the autism group, may include some misclassified cases the authors judged unlikely to alter the findings. Education data were less complete than health data because of biannual rather than annual collection, and the study’s descriptive design cannot establish the mechanisms, likely a combination of genetic loading and environmental factors, behind the observed risks.

The practical implications centre on a group the authors describe as often unidentified patients within their family systems. Sibling support groups have shown promise in reducing externalizing symptoms and improving coping skills, virtual mind-body groups have demonstrated acceptability among adolescents, and a systematic review identified eight psychosocial interventions targeting autism psychoeducation and sibling relationship quality, though more are needed. The authors argue for family-level screening within neurodevelopmental services, autism screening and proactive psychosocial supports across the broader family, and a shift in case conceptualization from the individual with a disorder toward the family system, even as long waitlists for such services across Canada remain a significant barrier. Replication in other samples, with more complete education data and sensitivity analyses censoring siblings with diagnosed neurodevelopmental disorders, will be important next steps.

Subject of Research: Mental health, medication and educational outcomes in siblings of autistic children compared with siblings of Down Syndrome and neurotypical probands

Article Title: Sibling Outcomes Among Probands with Autism Spectrum Disorder: A Population-wide Longitudinal Cohort Study

Article References: Katz, C., Spiwak, R., Tan, Q., Roos, L., McHardy, R. J. W., & Katz, L. Y. (2026). Sibling Outcomes Among Probands with Autism Spectrum Disorder: A Population-wide Longitudinal Cohort Study. Child Psychiatry & Human Development. https://doi.org/10.1007/s10578-026-02112-5

Image Credits: AI Generated

DOI: 10.1007/s10578-026-02112-5

Keywords: autism spectrum disorder, siblings, mental health, psychotropic medication, Down Syndrome, population-based cohort, suicide attempts, early childhood development, educational outcomes, administrative data, Manitoba, neurodevelopmental disorders