The link between insomnia and suicidal thoughts in patients with depression may be mediated by nightmares and dysfunctional beliefs and attitudes about sleep, research suggests.
"If true, our findings present novel targets for suicide prevention," say W Vaughn McCall (Georgia Health Sciences University, Augusta, USA) and colleagues.
"Treatment approaches for these targets might include either pharmacological or psychological approaches," they say, noting that "dysfunctional beliefs and attitudes about sleep have been shown to be modified by cognitive behavior therapy for insomnia."
The study participants were 50 patients with depression aged 20-84 years who were being treated as inpatients, outpatients, or in the emergency department. Seventy-two percent were female, and the most common diagnosis was major depressive disorder without psychosis (46%). Just over half of the patients had attempted to commit suicide at least once.
Psychometric test scores showed that depression was syndromal in 79% of the patients and of moderate intensity overall. An average Insomnia Severity Index score of 17.1 indicated a moderate degree of insomnia symptoms among the participants.
Depression severity, hopelessness, and the three sleep variables - insomnia severity, dysfunctional beliefs and attitudes about sleep, and disturbing dreams and nightmares - were all associated with suicide, as measured on the Scale for Suicide Ideation.
"Remarkably, none of the sleep variables were related to hopelessness," the researchers note. "This suggests that the three measures of sleep distress represent a different construct than what is included in the classic conceptualization of hopelessness."
A mediation analysis found that when insomnia and suicidal ideation were considered in isolation, insomnia was a predictor of suicidal thought. However, when disturbing dream and nightmare severity and dysfunctional beliefs and attitude severity were included, insomnia symptoms alone were not a significant predictor of suicidal ideation.
Speaking to the press, McCall said: "It turns out insomnia can lead to a very specific type of hopelessness, and hopelessness by itself is a powerful predictor of suicide.
"It's fascinating because what it tells you is we have discovered a new predictor for suicidal thinking."
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