The Physiology of Nightmares


New research reveals the presence of physiological changes in research participants while suffering from bad dreams.

While nightmares are experiences that everyone has heard of and most people have personally experienced at one time or another, for most people, nightmares are not frequent events. 

Stress and anxiety are known to be common nightmare triggers. The widely held explanation for this association is that unresolved worry and apprehension play out in the subconscious while an individual dreams. Even deeply buried fears are often manifested as bad dreams, especially during times of uncertainty. And it is well known that unsettling dreams do not always bear an obvious relationship to the real-life daytime problems, but may instead be represented by ‘proxy’ stories. 

Beyond the psychological issues, there is the question of whether there are systemic, biological changes associated with nightmares. New research reveals the presence of physiological changes in the hypothalamic hypophyseal axis among research participants who report suffering from bad dreams.

The physiology of nightmares

Interestingly, a small sample study demonstrated that women who reported nightmares were found to have a blunted cortisol awakening response on working days. Given the complex, multistage negative feedback loop involved between the hypothalamus, the blood vessels of the pituitary gland, and the adrenal cortex, this result suggests a diminished level of activity at some point in the neuroendocrine axis, but it is unclear at which level.

Another study, also relatively small, including a total of 65 patients who had an established diagnosis of attention deficit hyperactivity disorder (ADHD), revealed that the patients were approximately three times more likely to report nightmares than the control population. ADHD is a complicated condition, typically treated with prescription strength stimulants. While cortisol dysfunction is not necessarily implicated as a cause or effect of ADHD, it is interesting that the relationship between nightmares and ADHD may be related to the hypothalamic hypophyseal axis. Cortisol does have an overall excitatory effect on the body, although the impact of cortisol is not as fast acting as the stimulants used to treat ADHD. It is interesting, therefore, that an inherent deficit of stimulatory hormone levels had been associated with nightmares in more than one scientific research study. Physiologic hypostimulation then, may be an emerging area of study in the etiology of nightmares.

What to do about these findings?

For the neurologist, chronic nightmares are generally considered a psychiatric or psychological issue. Nightmares are more prevalent among individuals who suffer from posttraumatic stress disorder and other major anxiety disorders. However, the association between nightmares and physiologic changes is a fairly new finding. This is an important consideration in terms of the possibility of sustained neuroendocrine dysfunction as a result of nightmares. For the neurologist, patients who complain of bad dreams may be at an early stage of physiological dysfunction, and referral for counseling or psychiatric treatment could help prevent long-term neuroendocrine dysfunction.

How do you approach the management of nightmares?



Schredl M, et al. Nightmare frequency in adults with attention-deficit hyperactivity disorder. Eur Arch Psychiatr Clin Neurosci. 24 Mar 2016.

Nagy T, et al. Frequent nightmares are associated with blunted cortisol awakening response in women. Physiol Behav.  2015 Aug 1;147:233-237.

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