The role of sleep disturbance in the relationship between post-traumatic stress disorder and suicidal ideation

• PTSD symptoms indirectly predicted suicidal ideation via comorbid sleep disturbances, but had no direct effect.
• Polyvictimization predicted sleep disturbances and suicidal ideation independently of PTSD or major depression.
• No relationships were substantively altered after adjusting for comorbid major depression.

We tested if the risk of suicidal ideation in individuals with PTSD symptoms was dependent on comorbid sleep disturbance. Our cross-sectional sample included 2465 participants with complete data from the 21 year follow-up of the Mater University Study of Pregnancy (MUSP), a birth cohort study of young Australians. Using structural equation modelling with indirect pathways we found that 12 month PTSD symptoms did not directly predict suicidal ideation at 21 when adjusting for major depression symptoms, polyvictimization and gender. However, PTSD symptoms had an indirect effect on suicidal ideation via past-month sleep disturbance. Our results suggest that increased suicidal ideation in those with PTSD may result from the fact that PTSD sufferers often exhibit other comorbid psychiatric conditions which are themselves known to predict suicidal behaviours. Sleep disturbance may be targeted in those who experience PTSD to help prevent suicidal ideation.