In a study presented at the World Psychiatric Association international congress "Treatments in Psychiatry," scientists found that the more types of sleep disturbances people had, the more likely they were to have thoughts of killing themselves, engage in planning a suicidal act or make a suicide attempt.
"People with two or more sleep symptoms were 2.6 times more likely to report a suicide attempt than those without any insomnia complaints," said the study's leader, Dr. Marcin Wojnar, a research fellow at the Department of Psychiatry at the University of Michigan in the United States and Associate Professor of Psychiatry at the Department of Psychiatry at the Medical University of Warsaw in Poland.
The World Health Organization estimates that about 877,000 people worldwide die by suicide every year. The UN health agency says surveys indicate that for every death by suicide, anywhere from 10-40 suicide attempts are made.
"Identifying those at high risk of suicide is important for preventing it and these findings indicate that insomnia may be a modifiable risk factor for suicide in the general population," Wojnar said. "This has implications for public health as the presence of sleep problems should alert doctors to assess such patients for a heightened risk of suicide even if they don't have a psychiatric condition. Our findings also raise the possibility that addressing sleep problems could reduce the risk of suicidal behaviours."
Scientists have consistently linked sleep disturbances to an increased risk of suicidal behaviour in people with psychiatric disorders and in adolescents, but it has been unclear whether the association also exists in the general adult population.
In the study, the broadest and most rigorously conducted of its kind, scientists examined the relationship over one year between three characteristics of insomnia (difficulty falling asleep, difficulty staying asleep and waking at least two hours earlier than desired) and three suicidal behaviours (suicidal thoughts, planning and attempts) in 5,692 Americans. About 35 percent of those studied reported experiencing at least one type of sleep disturbance in the preceding 12 months.
The most consistent link was seen for early morning awakening, which was related to all suicidal behaviours. People with this problem were twice as likely as those with no sleep problems to have had suicidal thoughts in the preceding 12 months, 2.1 times more likely to have planned suicide and 2.7 times more likely to have tried to kill themselves.
Difficulty falling asleep was a significant predictor of suicidal thoughts and planning. Compared with people who reported no sleep problems, those who had trouble initiating sleep had 1.9 times the risk of suicidal ideas and 2.2 times the risk of planning suicide.
People who had trouble sleeping through the night - waking up nearly every night and taking an hour or more to get back to sleep - were twice as likely to have thought of suicide in the last year and were three times more likely to have attempted it than those who had no sleep problems.
The results were adjusted for several factors known to influence suicide, including substance abuse, depression, anxiety disorder and other mood disorders, as well as chronic medical conditions such as stroke, heart disease, lung disease and cancer. They were also adjusted for the influence of sociodemographic factors such as age, gender, and marital and financial status.
How sleep disturbance might increase the risk of suicide is still poorly understood, Wojnar said. Scientists have proposed that insufficient sleep may affect cognitive function and lead to poorer judgement, less impulse control and increased hopelessness. A dysfunction involving serotonin - a brain chemical involved in mood regulation that plays an important role in sleep, psychiatric disorders and suicide - is also suspected.
Further research is needed to determine whether other sleep problems, such as sleep apnoea (interrupted breathing during sleep) and non-restorative sleep, where people feel unrefreshed after an adequate amount of sleep, are also associated with suicidal behaviour, Wojnar added.