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Your dog looks up from his food bowl and speaks to you with the voice of your best friend. A lover you haven’t seen in years has appeared at your door with a bundle of roses. Or, perhaps, you’re screaming and flailing your arms and legs as you plummet from the top of the Eiffel Tower. Dreams can be moving, hilarious or terrifying by turn, but they are almost always absurd. It only adds to Freud’s mystique that he put stock in them as a source from which to draw serious inferences about a patient’s mental or physical health or true desires.

But was he so wrong? In recent years, the work of neuroscientists and data analysts has proved that the old dream analyst shrinks may have been onto something after all. No one knows exactly why we dream – though it seems that the process has something to do with memory consolidation – but most of the research carried out in recent years “validates the continuity hypothesis, that what you experience in real life is reflected in your dreams, and things that are more unconscious in the daytime become more explicit at night,” says Prof Luca Maria Aiello, a data scientist working at the IT University of Copenhagen in Denmark.

Prof Aiello’s work has also shown how our dreams are impacted by world events. One of his studies has shown that in America, nightmares were far more common in the 1960s than they are today, and they have slowly declined in frequency in the decades since, though they also became more common during the pandemic. “The general stress and anxiety in our environments certainly helps to influence our dreams and can make them more negative,” he explains.

Dr Abidemi Otaiku, meanwhile, a neuroscientist at Imperial College London who has also studied dreams, believes that some kinds of dreams serve to prepare us for adversity in the real world, while others reflect the processing of past events even though they may appear to be “completely random”.

While all of us like to think that our dreams are unique, some research indicates that 70 per cent of us have experienced the most common dream themes like falling, flying or losing our teeth – and broadly, any dream we may have can be sorted into one of just 40 different categories.

We asked the experts about the most common dreams and what they reveal about you.

Falling

When was the last time you encountered the edge of a cliff? Perhaps it was on a pleasant hike or a stroll around the coast. Having dreams about falling could reflect the fact that you are experiencing a high level of anxiety or overwhelm in your waking life – you have a lot on your plate, and so your brain is working overtime to prepare you for potential threats around the corner.

In the study of phobias, “there’s a theory called preparedness theory, which proposes that some people develop phobias of things that were dangerous to us in the ancestral past and are now ingrained in our brains,” says Dr Otaiku. “It’s just speculation, but perhaps what’s going on with dreams about falling is that our brains are preparing us to avoid this old threat.” That could explain why over half of people have had a falling dream, according to one survey.

People with anxiety disorders have been shown to have a greater volume of negative dreams where they feel out of control. So if you’re regularly dreaming about falling, it may be time to seek support for your anxious feelings. The same goes for dreams about being chased or fighting people off.

“It’s not easy to draw the line between what’s just a bad dream and what’s a nightmare, but people who score higher in levels of neuroticism and anxiety are more likely to have more nightmares, and so are people who have experienced traumatic events,” says Dr Otaiku.

Losing your teeth

It’s long been said that dreams about losing your teeth also result from anxiety. About two in five people have had them. Different cultures around the world have different explanations, given how commonly they pop up: in China, dreams about tooth loss are associated with lying or deceit, while the ancient Greeks thought they symbolised financial ruin, and the Native Americans took them to be a warning that death was close.

There is a more simple explanation. When we sleep, the brain’s “ability to tell what’s going on in the world around you”, sometimes referred to as exteroception, is reduced, but not completely lost, says Dr Otaiku. People who are stressed in the daytime may grind their teeth as they sleep, prompting dreams about tooth loss when the brain picks up this movement – hence the old adage that dreaming of lost teeth is a sign of bad things to come, as they may be prompted by daytime stressors you’re already facing. “There’s some research to show that frequent dreams about tooth loss are linked to oral health, but the association is quite weak – it’s not the most robust evidence,” Dr Otaiku adds.

Failing to prepare for a big exam

In our modern world, we do not often need to deal with life-endangering threats. Therefore the most stressful events of our lives may be encoded into our psyches as a source of true danger – particularly if they occurred in our early years.

Cue the exam anxiety dream: “People in their 50s and 60s, who haven’t had to sit exams in decades, often still have them [as a response to stress],” Dr Otaiku says. “The brain is more likely to register things that are very salient, which is also why trauma can reoccur in dreams so frequently.” One study has found that 34 per cent of people have had a stressful dream like this.

“Perhaps those people [who have exam dreams] are more conscientious, which makes them study more,” says Dr Otaiku. “It’s hard to say. But in older people who are dealing with stress, that might manifest in dreams about exams.”

Having an effective bedtime routine, where you avoid stressors like your email inbox or strained conversations right before bed, could help to reduce the frequency of these dreams.

Cheating on your partner

Sex dreams are very common, though they wane in later life. Dreaming is a process that’s closely connected to our hormones, so it’s no wonder that they are such a common feature of adolescence. Seventy to 80 per cent of us have had one over the course of our lives, and around 30 per cent of men and 13 per cent of women report that they still have some sex dreams past the age of 50, according to one study.

Within that, dreams about cheating on your partner and the panic, shame or guilt that follows are also common. Nearly a quarter of us have had a dream about being unfaithful to our partners or discovering an affair ourselves, the results of one survey show.

One the one hand, it might be that your brain is chewing over a recent sexual experience you’ve had, or processing your attraction to a stranger over the course of your waking day. But it also may be a sign that something needs to change in your relationship.

“Dreams are often connected to strong emotional experiences or worries that you have in the day,” says Prof Aiello. Your subconscious might be telling you something that you aren’t ready to accept – or it could be totally random. The point is that “getting more familiar with your dreams, perhaps by keeping a dream journal or talking about them more, can be valuable in helping you to reflect on your life”.

Flying

Flying dreams are believed to occur in about 40 per cent of people, usually in early life. Some research indicates that frequent dreams about flying are associated with personality traits like being more open to experience and less neurotic than the general population.

People who remember their dreams more easily are also more likely to have dreams about flying, a trait that, along with the other personality indicators, is also linked to lucid dreaming, where you’re aware that you’re dreaming despite being asleep.

Though these dreams are fantastical, their origins are likely quite ordinary. “When you’re asleep, your body’s ability to work out where it is in space is reduced, and the frontal lobes, which are involved in rationality, are switched off,” says Dr Otaiku. “This is part of why we can have dreams that are so spectacular.”

Are bad dreams linked to dementia?

“My research has shown that people who have more frequent nightmares at any age in life may be more likely to develop dementia in the future,” Dr Otaiku says, and this association was not entirely explained “by depression, anxiety, or other types of coexisting sleep problems like insomnia, which suggests that nightmares have a direct link to dementia”.

One study carried out by Dr Otaiku indicates that children who experience nightmares are more likely to develop cognitive impairment (a precursor to dementia) even 50 years later. Another study, of 3,000 adults in America, found a link between nightmares in middle-aged adults and the likelihood of a dementia diagnosis ten years later.

Dr Otaiku has also found that frequent nightmares can increase the pace of ageing. “It is possible that part of the connection between nightmares and future dementia could be because those with more frequent nightmares are ageing faster biologically, and of course, older age is the greatest risk factor for developing dementia.”