What causes nightmares in adults — and what actually helps

Occasional bad dreams are universal and mean nothing. Nightmares become a medical matter when they are frequent, vivid, distressing enough to wake you, and start to bleed into waking life — dread of going to bed, daytime exhaustion, low mood. That pattern is called nightmare disorder, and the short answer to "what causes it" is that in adults it rarely arrives out of nowhere: it usually travels with something else, above all trauma. The more useful news is that the best-supported treatment is a technique you do while awake, not a pill. This is an explainer, not medical advice.

How common it is

Nightmare disorder affects approximately 4% of adults, according to the American Academy of Sleep Medicine's position paper on the condition [s1]. It occurs either on its own or as part of another disorder — most commonly post-traumatic stress disorder, where distressing dreams are a core symptom [s1]. That framing matters: for a large share of adults with a serious nightmare problem, the dreams are one thread of a broader condition rather than a stand-alone fault in sleep [s1].

What causes them

Nightmares are dreams that occur mostly in REM sleep, the stage richest in vivid imagery, and anything that destabilises or intensifies REM can bring them on. In adults the recurring drivers are trauma and PTSD, in which the dreams often replay or echo the traumatic event; psychiatric conditions such as anxiety and depression; and stress. Medications and substances are an underrated cause — certain drugs acting on brain chemistry, and alcohol or withdrawal from it, can all provoke nightmares — which is why a review of what someone is taking is part of any proper assessment. The point is that recurrent adult nightmares are usually a symptom pointing somewhere, not a random misfire.

What actually helps

Here the evidence is clearer than for most sleep complaints. The AASM position paper singles out one treatment as "recommended" for both PTSD-associated nightmares and nightmare disorder: image rehearsal therapy [s1]. It is a brief cognitive-behavioural technique in which, while awake, you take a recurring nightmare, deliberately rewrite it with a new, less threatening storyline, and mentally rehearse the new version — gradually loosening the grip of the old one. It is the only therapy the paper places in its top tier [s1].

A long list of other options sit one rung down, as treatments that "may be used" because the evidence or expert consensus is less clear-cut. For nightmare disorder these include cognitive behavioural therapy; exposure, relaxation and rescripting therapy; hypnosis; lucid dreaming therapy; progressive deep muscle relaxation; and, among drugs, prazosin and triazolam [s1]. For PTSD-associated nightmares the "may be used" list is longer still, spanning CBT, CBT for insomnia, eye movement desensitisation and reprocessing, and a range of medications including prazosin [s1].

Two things are explicitly not recommended for nightmare disorder: the sedatives clonazepam and the antidepressant venlafaxine [s1]. The paper is careful to note that its lists are alphabetical, not ranked by preference, and that the final decision always rests with a clinician weighing the individual patient [s1].

The shift in the evidence

The position paper updated an earlier AASM best-practice guide from 2010, which had already identified image rehearsal therapy and prazosin as leading options [s2]. The direction of travel since then has been to keep a psychological technique at the front and to become more cautious about drugs — prazosin, once widely prescribed for trauma nightmares, was moved to the "may be used" category as later trial results proved more mixed [s1]. For how that specific evidence on prazosin has evolved, see prazosin for nightmares in PTSD.

When to see a doctor

Frequent nightmares that wreck your sleep, leave you dreading bed, or follow a traumatic event are worth raising with a clinician — both because effective treatment exists and because they can be a window onto PTSD, depression or a medication problem that deserves attention in its own right. Sudden new nightmares after starting a drug are a specific prompt to ask whether the two are connected.

Why it matters

Adult nightmares are often dismissed as trivial, yet for the 4% with nightmare disorder they are both treatable and revealing [s1]. The headline is unusually encouraging for sleep medicine: the best-evidenced treatment is learning, while awake, to rewrite the dream [s1][s2].

Sources

• Position Paper for the Treatment of Nightmare Disorder in Adults (AASM) — Journal of Clinical Sleep Medicine, 2018-06-15
• Best Practice Guide for the Treatment of Nightmare Disorder in Adults — Journal of Clinical Sleep Medicine, 2010-08-15