Autistic Traits and Suicidal Thoughts, Plans and Self-Harm in Late Adolescence: Population Based Cohort Study

Background:

The potential role of suicide as a contributor towards the excess premature mortality in people with autism has been highlighted recently. However there is relatively little understanding about which features of autism may lead to suicidal thoughts and behaviours and whether there are any potentially modifiable mediators. Existing research is largely limited to case reports or small clinical samples and there is a need for longitudinal, population based studies to provide further insights into the burden and pathways of suicidal thoughts and behaviours in autism.

Objectives:

Study objectives were two-fold: i) to examine the association of trait measures of autism with suicidal and self-harm behaviour at age 16 years; ii) to examine whether any associations could be explained by depression in early adolescence at age 12 years.

Methods:

Participants were 5,034 members of the Avon Longitudinal Study of Parents and Children (ALSPAC), a UK population-based birth cohort who completed a postal questionnaire on self-harm with and without suicidal intent, as well as suicidal thoughts and plans at age 16 years. Four autistic trait measures were analysed. These included the coherence subscale of the Children’s Communication Checklist (assessed at 9 years), the Social and Communication Disorders Checklist (measured at 8 years), a repetitive behaviour measure (assessed at 6 years), and the sociability temperament subscale of the Emotionality, Activity and Sociability scale (measured at 3 years). These measures were dichotomised, with approximately 10% defined as the autism ‘risk’ group. Multinomial and modified poisson regression analyses were used to examine the associations between autistic trait measures and suicidal and self-harm behaviour at age 16 years. Structural equation modelling (SEM) was used to examine whether depression in early adolescence, as measured by the moods and feelings questionnaire (SMFQ) at 12 years, may explain this association. Analyses were adjusted for a range of child, parental and familial confounding factors.

Results:

Impaired social cognition at age 8 years was associated with increased risk of suicidal (adjusted OR=2.14, 95% CI 1.28 to 3.58, p=0.004), but not non-suicidal self-harm (adjusted OR=1.02, 95% CI 0.62 to 1.67, p=0.943) at age 16 years. Impaired social cognition was also associated with suicidal thoughts (adjusted OR=1.43, 95% CI 1.06 to 1.92, p=0.019) and plans (adjusted OR=1.95, 95% CI 1.09 to 3.48, p=0.024). There was no evidence for an association between the other autistic traits and self-harm with or without suicidal intent, suicidal thoughts and/or plans. Approximately 40% of the total estimated association between impaired social cognition and self-harm with suicidal intent was explained by depression in early adolescence.

Conclusions:

Impairments in social communication were strongly associated with suicidal thoughts, plans and behaviours at age 16 years. A substantial proportion of this effect was explained by depressive symptoms. These findings suggest that the social impairments associated with autism may be important in relation to suicidality, and that identification and treatment of depression may have the potential for preventative action.