Nightmares: what they are, why they happen, and what to do about them

In sleep medicine, a nightmare is a bad dream that wakes the person up. An unpleasant dream you don't wake from doesn't technically count, though in everyday speech we use the word for both. Nightmares happen mostly in REM sleep and are more common in the second half of the night.

They shouldn't be confused with night terrors. Those occur in non-REM sleep, in the first half of the night, and the person usually doesn't fully wake and doesn't remember the episode. They're different things with different treatment.

Nor are nightmares predictions. A nightmare in which someone dies or something terrible happens doesn't announce that it will. It describes the dreamer's emotional state.

According to the Sleep Foundation, between 2% and 8% of adults have trouble with nightmares. They're more common in childhood, especially between ages 3 and 6, and women report them more, from adolescence to middle age. In one study, 47% of college students had had at least one in the previous two weeks. In other words: occasional nightmares are normal.

There's no single explanation. They're linked to emotional processing and memory, and several risk factors are identified:

• Stress and anxiety.
• Post-traumatic stress disorder.
• Certain medications or substances, or stopping ones that suppressed REM.
• Sleep deprivation, which causes REM rebound and more intense dreams.
• Family history or frequent nightmares in childhood.

If the nightmares began with a new medication, mentioning it to your doctor comes first.

From the Onirah method's point of view, a nightmare isn't a warning, it's a dream with the volume at maximum. The mind turns up the tone when a worry hasn't found room during the day. That's why the fear is intense while the content is often recognisable: things that already worried you, in exaggerated costume.

Some very common themes, and the question they tend to open (always in the conditional):

• Being chased: it tends to speak of something avoided. What have I been dodging for a while?
• Falling: it tends to speak of lost control or lost support. Where do I feel I have no ground?
• Death: it almost never speaks of dying; it tends to speak of endings and change. What stage is closing?
• Snakes: they tend to speak of change or something uncomfortable. What is moving?

For the full method, see the interpretation guide.

Occasional nightmares usually need no treatment. What helps make them less frequent is mainly looking after your sleep:

• Regular bed and wake times.
• Avoiding caffeine and alcohol at night.
• Cutting screens before bed.
• Sleeping enough, because sleep deprivation favours intense dreams.

And as a reflection exercise, lower the drama in writing: note the nightmare on waking, describe what you felt, what exactly scared you, and what it resembles in your waking life. Writing it takes it out of your head and turns it into text, which is less frightening. A dream journal is a good tool for that.

Important: this is reflection, not treatment. You also don't have to sit in the dark with the fear: if a nightmare leaves you unsettled, turning on the light, drinking some water, airing the room or telling someone in the morning are reasonable ways to lower the volume. For nightmares that repeat often, a professional consultation is the recommended route.

The Sleep Foundation says to see a doctor if nightmares:

• happen more than once a week,
• affect your sleep, mood or daily activities,
• began when you started a new medication.

When nightmares are frequent and impair sleep, mood or daily life, it's called nightmare disorder, a parasomnia much less common than occasional nightmares. There is treatment for it. The American Academy of Sleep Medicine's best-practice guide (2010) recommends imagery rehearsal therapy at its highest level of evidence: the recurring nightmare is rewritten with a different ending and rehearsed while awake. It's done with a professional, not improvised. If nightmares keep returning after a trauma, that's also a reason to seek help sooner rather than later.

Keeping a dream journal can help your doctor see the frequency and impact, and it's a good way to prepare for the appointment.

If you decide to consult, going prepared saves time and helps you be understood. The Sleep Foundation suggests that a sleep journal can show your doctor how often nightmares happen and their impact. You can bring notes on:

• How often they happen (times per week) and since when.
• How they affect your day: whether you struggle to sleep out of fear, whether you're more tired or irritable.
• What changed when they started: a new medication, a stressful period, a difficult event.
• A couple of examples written straight after waking, unpolished.

You don't need to interpret anything. That's reflection work, which can come later and separately.

A widespread idea is to learn lucid dreaming to change nightmares from inside. The Sleep Foundation reports preliminary signs it might reduce recurring nightmares, but the evidence is mixed and limited, and the 2010 guide treats it only as an option with low-grade evidence. Lucid nightmares also exist: knowing you're dreaming doesn't guarantee you can get out.

It's not a substitute for treatment. If you're suffering, start with what has backing.