(Photo: María Victoria Heredia Reyes/Unsplash)

Neurotic people, by definition, spend much of their lives in a dark mood. Given the positive emotions are associated with good health, it's reasonable to assume that all that guilt, anger, and anxiety will eventually lead to an early grave.

Well, surprise: A sizable new study from Great Britain reports that, for many neurotics, the opposite is true.

Among two large subsets of participants, "higher neuroticism was associated with reduced mortality from all causes," writes a research team led by Catharine Gale of the University of Edinburgh.

This welcome effect apparently depends upon how one's neuroticism manifests, and what actions it propels you to take.

The study, published in the journal Psychological Science, featured 321,456 people who were registered in the U.K. Biobank, a health-related resource designed to determine the causes of disease in middle-aged and older people. All were between the ages of 37 and 73 when they enrolled between the years 2006 and 2010.

Participants filled out a standard questionnaire identifying neuroticism. They also rated their health on a scale from "excellent" to "poor," and reported whether they engaged in various health-related behaviors, including smoking, drinking, and exercise.

If you have pre-existing health issues—or at least think of yourself as an unhealthy person—neurotic tendencies seem to have a protective effect against premature death.

By the end of the study period, in June of 2015, 4,497 of them had died. Using official death certificates, the researchers noted the cause of their demise.

They report that "higher neuroticism was associated with lower mortality," both in general and due to cancer, cardiovascular disease, and respiratory disease. But this was true "only in those people with fair or poor self-rated health."

In other words, if you have pre-existing health issues—or at least think of yourself as an unhealthy person—neurotic tendencies seem to have a protective effect against premature death.

This was "not explained by the health behaviors we assessed (smoking, exercise, fruit and vegetable intake, and alcohol consumption," Gale and her colleagues write. So what does explain it?

"It may be that individuals with higher neuroticism are more vigilant about their health if they perceive it to be less than excellent," they write.

The researchers also delineated between two types of neuroticism. People who gave strongly affirmative answers to such questions as "Would you call yourself a nervous person?" and "Would you call yourself tense or highly strung?" were labeled "anxious-tense."

Those with high scores on another group of questions, including "Are your feelings easily hurt?" and "Are you ever troubled by feelings of guilt?" were classified as "worried-vulnerable."

No matter their self-reported health, "Higher scores on the worried-vulnerable facet were associated with a reduced risk of death from all causes," they write. However, this was not true among those in the "anxious-tense" category; their form of neuroticism was not related to mortality either way.

If you assume that worried people make more visits to the doctor, this finding adds weight to the aforementioned heightened-vigilance thesis. "The propensity to seek medical help in response to worries about health could plausibly result in earlier identification of cancer, and greater likelihood of survival," the researchers note.

So if you're fretting about that darkened patch of skin on your arm, it might drive you crazy—but it could also propel you to the dermatologist, who can remove it if your worst fears turn out to be true.

Of course, that depends on whether you have access to health care, which is a different worry altogether.