This article in the Journal of Clinical Sleep Medicine discusses the relationship between nightmares, beliefs about sleep and insomnia, and suicidal thoughts. Apparently, studies have shown that insomnia symptoms are related to near lethal suicide attempts. Nightmares are also linked to suicidal thoughts and completions.
This study gave questionnaires to patients that presented with suicidal thoughts or attempts. Insomnia symptoms were common in these patients. Nightmares were also present. These symptoms remained significant even after adjusting for the effects of depression - which can increase risk of suicide and insomnia. The researchers analyzed these patients thoughts and beliefs about sleep and insomnia - such as, "if I don't sleep well, I will not be able to function at all the next day."
The findings suggest that the insomnia symptoms themselves were not the determining factor for suicidal thoughts - it was the thoughts about the consequences and causes of insomnia that was related to suicidal thoughts. Nightmares also increased the risk of being suicidal. This makes sense. Many people wouldn't mind insomnia as much if they felt it didn't impact their daytime functioning or possibly affect their health. The researchers noted a sense of hopelessness about insomnia - meaning these insomniacs did not think they ever would sleep better. And therefore, their daytime functioning and how they felt in the daytime would never improve. It reminds me of patients that deal with chronic, unrelenting pain - they can become hopeless about ever living a life without pain.
Unlike chronic pain, however, insomnia can get better with behavioral therapy. Recognizing this is important for physicians and mental health workers, so that they can refer their at risk patients with insomnia for appropriate treatment.