Depression and anxiety, as well as severe mental disorders such as schizophrenia, have become more openly discussed in society. Yet, one aspect of mental health remains largely in the shadows: Nightmares.

Not just the product of children's over-active imaginations, about 5% of adults experience frequent nightmares. A study published in 2001 demonstrated that men who suffered from frequent nightmares were more likely to commit suicide than those who did not. However, the study included war veterans, a group who suffers more frequently from nightmares compared to the general population, most likely as a result of PTSD.

So, a new team of researchers wanted to separate veterans from civilians and reanalyze the data. In a new study (whose lead author has the surname "Sandman," appropriately enough), the team stratified and expanded the original paper by adding new data, for a total of 69,101 participants aged 25 to 74. The volunteers answered whether they "often," "sometimes," or "never" suffered from nightmares. Some of their results were surprising.

Results Replicated

As expected, war veterans had the highest prevalence of frequent nightmares, with a rate of 7.6%. Interestingly, among the whole population, more women (4.8%) suffered from frequent nightmares than men (3.4%).

Just as the original study showed, nightmares predicted suicide. Those who suffered nightmares frequently or occasionally were 84% or 33% more likely to commit suicide, respectively. But when war veterans were removed from the analysis, the results did not change. Therefore, in society as a whole, frequency of nightmares serves as a risk factor for suicide.

Among war veterans, the team's results were unexpected. They hypothesized that a link between nightmare frequency and suicide would be even stronger among this group. While the link did persist, it was much weaker and/or statistically insignificant, possibly due to small sample size. Further analysis showed that veterans who suffered from insomnia, depression, or permanent disability during the war or abused alcohol were likelier to have nightmares.

Limitations

The authors admit a couple major limitations to the study. First, war veterans were answering these questions three decades after the conclusion of WWII. It is quite possible that veterans who were suffering greatly from PTSD had already killed themselves. Second, though women suffered more frequent nightmares than men, men (by far) were more likely to commit suicide than women. And though veterans suffered more frequent nightmares than civilians, the suicide rates were comparable. So, nightmares are not a strong predictor of suicide.

Still, a patient suffering from frequent nightmares could serve as a warning flag for psychiatrists and therapists.

Source: Nils Sandman, et al. "Nightmares as predictors of suicide: an extension study including war veterans." Sci Rep 7:44756. Published: 15-Mar-2017. DOI: 10.1038/srep44756