You wake up in the morning from a frightening dream.
“Is this a sign that something bad is going to happen?”
“Does this dream mean something?”
Some of you may have found yourselves searching online for dream interpretations because you couldn’t stop wondering.
Dreaming of a snake means money is coming, dreaming of losing your teeth reflects anxiety, being chased in a dream is a sign of stress…
There are all sorts of interpretations, but is there any scientific basis for reading a person’s inner state or future from the content of their dreams?
Professor Masashi Yanagisawa of the University of Tsukuba, a leading figure in sleep research, has given a fairly clear answer to this question.
Professor Yanagisawa’s Answer: “It’s Safe to Say Flatly That There Is None”
In January 2026, Professor Yanagisawa was asked about dreams on TBS’s news program N Star.
When asked a question to the effect of, “There’s also dream interpretation. Do dreams hint at our inner state, or anything like that?”
“It’s safe to say flatly that they don’t.”
was his reply.
In other words, there is no confirmed scientific evidence supporting the one-to-one interpretations often found in dream reading, such as “Because you had this dream, X will happen” or “This dream is proof that your state of mind is X.”
Of course, dreams can reflect our experiences, emotions, and memories from the day.
But that is a separate matter from the idea that “a particular dream has a fixed meaning.”
Just because you had a bad dream, there seems to be no need to worry that it’s an omen of something bad.
Why Do We Dream in the First Place?
In fact, there is still a great deal about dreams that science doesn’t yet understand.
According to Professor Yanagisawa, dreams with vivid stories and emotions occur mainly during REM sleep.
In REM sleep, parts of the brain are about as active as when we’re awake, while the body remains asleep, a distinctive state.
And what Professor Yanagisawa emphasizes is that
“REM sleep = shallow, poor-quality sleep” is not true.
REM sleep is also a necessary part of our sleep, and there’s no need to think of vivid dreaming in itself as “proof that you didn’t sleep well.”
In another commentary from September 2026, he explained that we dream around four to five times a night, but we usually forget most of those dreams, and we only think “I had a dream” about the ones we happen to remember.
So Why Do We Have Unpleasant Dreams?
This is where dreams get interesting.
While dream interpretation has no scientific basis, “Might dreams themselves serve some kind of function?” is a question research continues to explore.
One idea is the “Threat Simulation Theory.”
Put simply, it’s the idea that by simulating dangerous situations in our dreams, the brain may be “rehearsing” for when we encounter danger in the real world.
In fact, past research has reported that children who experienced severe threats had more threatening events in their dreams.
Professor Yanagisawa has also introduced the idea that negative dreams may be a rehearsal for “really bad situations” that could happen in real life, and that this may be related to how we cope with stress.
However, this is one hypothesis that is still being studied.
Some studies have reported results that don’t fit the threat simulation theory, and it has not been established that “nightmares serve as a rehearsal for danger.”
Remembering a Dream Doesn’t Mean You Slept Lightly
“I had lots of dreams last night, so I must have slept lightly.”
This is another thing we often hear.
But Professor Yanagisawa explains that REM sleep is by no means “light sleep” in the simple sense, but important sleep.
Even more interesting, having a dream and remembering a dream are not the same thing.
We dream many times while we sleep, but we forget most of those dreams after we wake up.
That’s why
“I don’t remember any dreams = I didn’t dream”
“I remember my dreams = I slept lightly”
aren’t judgments we can make so simply.
There’s no need to decide whether you slept well or poorly based only on whether you dreamed.
Even After a Bad Dream, “I’m Glad It Was Only a Dream” Is Enough
At present, there is no scientific support for using dream interpretation to pin down someone’s future or state of mind, as in “this dream means X.”
On the other hand, researchers around the world are studying how dreams themselves relate to memory, emotion, and brain activity during sleep. The relationship between dreams and memory consolidation is also being studied, but so far the results have not been consistent.
In other words,
“Dream interpretation has no scientific basis” ≠ “Dreams have no meaning at all”
That’s an important distinction.
Why do we dream?
Why do we sometimes remember unpleasant dreams more vividly than happy ones?
Precisely because so much is still unknown, dreams may be one of the most fascinating topics in sleep science.
Professor Yanagisawa says there’s no need to worry too much about bad dreams, and sums it up in very simple words:
“Just think, ‘I’m glad it was only a dream.'”
Even on a morning when you wake from a scary dream, rather than worrying all day that “it might be a sign of something,”
“I’m glad it was only a dream.”
Thinking that way and starting your day as usual may be just the right approach.
At La HEAD, we will continue to share everyday questions about sleep and the brain, based on scientific research and expert explanations.