What Are Dreams?
Dreams are sensory experiences that unfold during sleep. They are mental episodes of seeing images, hearing sounds, or feeling bodily sensations. Dreams sometimes contain a storyline but are also perceived as non-narrative collections of disconnected images [1, 2].
Dreams are a complex mental experience with a rich phenomenology involving percepts, thoughts and emotions; they include perception-like elements, which may be hallucinatory and, in particular, are characteristically visual and motoric. Furthermore, dreams are typically triggered by negative feelings. Finally, despite their peculiar and distorted nature, people experience these painful dreams as being ‘as if’ they were veridical, that is, as if they were happening while they were sleeping [3].
Dreams also reflect our brain's activity during sleep. They show that disconnected from the environment, our brain can generate an entire world of conscious experiences by itself [4].
Dreams occur through several distinct stages of sleep, but we experience most during REM sleep [2]. Most people dream for about 2 hours per night, and while it used to be believed that we only dream during REM (rapid eye movement) sleep, more recent research finds that we do dream during other stages of sleep, too [2].
Dreams during REM sleep tend to be longer, more vivid, story-like, and more bizarre than those during non-REM (NREM) sleep [3].
What Are The Causes Of Dreams?
Dreams are a fascinating aspect of our sleep cycle, and while the exact causes are not fully understood, several theories and contributing factors have been identified.
One theory holds that they help the brain process and file away specific memories while discarding others [3, 5]. If this is correct, dreams directly impact memory consolidation and play an important, if disorienting, role in our healthy sleep. The most common form of dreaming occurs during the rapid eye movement (REM) sleep cycle, a phase associated with memory processing. REM usually cycles every 90 minutes through a night of sleep, lasting 20 to 25 minutes on average [5].
Stress and anxiety are also known to trigger intense dreams. Difficulties in daily life, problems with friends, family, school, or work, and significant events like getting married or buying a house can all contribute to vivid dreams [5]. Traumatic events, such as the death of a loved one, sexual abuse, or a car accident, can also cause vivid dreams [5].
Sleep disorders such as insomnia and narcolepsy can increase the risk of vivid dreams, as can alterations to a person’s sleep schedule – whether that’s flying overseas (and thus sleeping at a different time) or getting insufficient sleep [5].
Some medications, such as many antidepressants, beta-blockers, antihypertensive drugs, Parkinson’s disease drugs, and smoking cessation drugs, can lead to vivid dreams [5]. Drinking too much alcohol, recreational drug use, or being addicted to or withdrawing from drugs can lead to vivid dreams, usually nightmares [5].
Can Dreams Be Dangerous?
There’s no denying that dreams can lead to health warnings – and not just for the risk of nightmares beleaguering our mental and physical health. Chronic nightmares have been found to arise in as many as 70% of people with post-traumatic stress disorder (PTSD), major depression and other mental health diagnoses [6].
Nightmares have also been linked to suicidal behaviour, over and above other psychiatric risk factors, including depression, anxiety and PTSD [7]. Researchers found that having regular nightmares increased suicide risk, even correcting for the war experience [8].
Although lucid dreaming is typically a safe activity, individuals with mental health disorders are more at risk of experiencing harmful outcomes like sleep disorders, depression, anxiety, derealisation and dissociation [9].
Sleepwalking, too, is often a dangerous dream outcome – in one study of 100 patients with a history of recurring sleepwalking episodes, 57.9% had been injured or had caused injuries themself [10].
Can You Die From Dreams?
Dreams, including nightmares, are a normal part of the healthy sleep cycle and human brain function and are often shaped by stress, anxiety or previous traumatic experiences. There is no scientific basis for the belief that you can ‘die from a dream’. Even if a dream includes negative, frightening, or final experiences, it doesn’t predict or cause physical damage or injury [11].
However, dreams can also be highly emotional. Nightmares, for example, are a diagnostic symptom of post-traumatic stress disorder (PTSD) [11], and dreams containing themes of death can be distressing for psychologically vulnerable individuals, as may be the case for those with major depressive disorder (MDD) [12]. Professional help should be sought in such instances.
Extreme emotional stress induced by nightmares is also the reported trigger of immediately life-threatening cardiac events in people whose hearts show no evidence of underlying coronary artery disease [13]. But this isn’t because of the dream itself; it’s because of the emotional response it activates.
In conclusion, even though experiencing nightmares, particularly distressing dreams, can be very emotionally upsetting and suggest associated mental health problems, unfortunately, dreams are unlikely to directly cause disease or premature death. If you intermittently or continually have distressing dreams or nightmares, please seek the help of a healthcare professional.