This studied the relationship of insomnia on suicide risk by considering both sleep duration & depression.
The study was based on a Swedish prospective cohort of >38k participants with a mean follow-up time of 19 years.
Sleep disturbances have been identified in previous work as an early & important marker for suicidal behaviour and insomnia has been shown to be an independent risk factor for suicidality.
Results:
Insomnia was found to be associated with suicide risk, but only amongst short sleepers. This is in contrast to no significant association being observed amongst sleepers of 7 hours per night or more.
Difficulty initiating sleep was most strongly associated with rusk of suicide amongst the nocturnal symptoms.
For baseline information on the study population, insomnia was more common among women than men. Compared to subjects without insomnia, people with insomnia had shorter sleep duration & more depressive symptoms.
Furthermore, people with insomnia were more likely to be older, less educated, higher BMI, reported lower physical activity & had more often been diagnosed with cancer or CVD.
The link b.t. insomnia & suicide risk became more pronounced with decreasing depressive symptoms. People without depressive symptoms who suffer from insomnia may be at an elevated risk of developing depressive episodes & thus may be at a higher risk of committing suicide compared to non-depressed people without insomnia. However, the authors note that their findings suggest a ceiling effect of the impact of insomnia on suicide risk.
The association b.t. insomnia & suicide risk becomes more pronounced with decreasing depressive symptoms.
Use of hypnotics at baseline was highly correlated with insomnia complaints, short sleep and depression and suicide. However, when the analyses are focused on only those who reported no hypnotic use, similar findings were observed.
Snoring heavily was significantly associated with insomnia complaints, short sleep & depression, but wasn’t associated with suicide.
In discussing the association between short sleep, insomnia, depression and suicide risk, the authors note that additional research is needed to elucidate the shared neurobiological pathways. However, they discuss the known links with impaired sleep on cognitive function & emotional regulation.
In concluding, the authors state that “Abnormalities of sleep duration and insomnia symptoms should be evaluated when assessing suicide risk”. Further, insomnia with short sleep increases suicide risk both directly but “also indirectly by increasing the onset or reoccurrence of depression” (p4).
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