Why do so many people have the same dreams?

October 12, 2012 2:25 PM

Are there any physiological explanations for why so many people have the same dreams?

Just a few examples: teeth falling out or crumbling, ending up back in school because of a class you forgot to attend or an exam you failed, Mouth full of gum - you pull and pull but can't get it all out, unable to dial a phone, trying to run but barely able to move... I could go on, but you get the idea!

I'm just wondering if there are any non-Jungian or any physiological explanations for any of this. Not particularly interested in "dreams about teeth falling out represents fear of death" explanations - more interested in explanations like "dreams about teeth falling out happen more often among people who grind their teeth in their sleep" (though if you have good evidence or interesting information about the psychology of dreams, then by all means put it out there!)

posted by cilantro to grab bag (22 answers total)

For me and another family member, dreams of running and running are induced by episodes of low blood sugar. (I think the school dreams are metaphorical. But running dreams can be physiogically based, an interpretation of the higher heart rate and other symptoms associated with low blood sugar.)
posted by Michele in California at 2:30 PM on October 12, 2012

Trying to run but unable to move sounds like it's closely linked physiologically to a recurring dream of mine, trying to scream but no noise comes out. I've always been under the impression that both were due to sleep paralysis.
posted by telegraph at 2:45 PM on October 12, 2012

I don't know if there are physiological explanations, but it seems like there are obvious cultural explanations.

For example, the classic school/exam dream. Tests in school are probably the first high-pressure performance situation that most middle class Americans face. And so if you're going to have a dream where you're put on the spot in a stressful way, you go straight back to the classroom.

A lot of "typical" dreams are about occurrences common in our culture, or areas where a lot of people attach the same feelings and significance to that particular thing. Think of how common it is to be afraid of the dentist. You can go out a lot wider, culturally speaking, for the significance of the classic "running from something scary but can't get away" dream. I mean, they call it "fight or flight" for a reason, right?
posted by Sara C. at 2:45 PM on October 12, 2012 [1 favorite]

You may be interested in: Ever Dream This Man?
posted by phunniemee at 2:46 PM on October 12, 2012 [3 favorites]

The teeth dreams have only occured to me when I was about to have a dental procedure done - before wisdom teeth surgery, root canal and regular check ups with the dentist (while I was near-phobic about dentists; since I got that under control, the dreams don't occur anymore previous to check ups). I never had any teeth-related dreams if there was no upcoming appointment. Same for my entire family - teeth dreams are always linked to actual encounters with dentists, and due to my family's notorious issues with wisdom teeth, it's quite a set of data.
Therefore, I would suspect that teeth dreams are common because fear of dental treatments is rather common, too. You don't hear about people being anxious about seeing a dermatologist or something; it's either doctors in general - or dentists only. In other words, a common fear results in many people having similar dreams about it.
posted by MinusCelsius at 2:53 PM on October 12, 2012

MinusCelsius - interestingly, I have tooth loss dreams all the time, but I've never had a cavity or any dental work - just the standard non-traumatic yearly cleaning. I look forward to it!
posted by cilantro at 2:57 PM on October 12, 2012

Is there any evidence that many people do indeed have these dreams? I've never had any of those dreams. I feel left out. :(
posted by stray at 3:15 PM on October 12, 2012 [3 favorites]

Yeah, I think the anxiety dreams (whether school-related or the oh god I'm naked type) are culturally influenced. You feel anxious, it manifests in your dream as something you've frequently felt anxious about (school, social interactions, work, etc).

As for physiological explanations, not sure about any science to back this up, but I've generally assumed any dreams involving an inability to move or speak, or dreams about a difficulty in performing an easy physical task have a root in sleep paralysis and the deeper phases of sleep where your body doesn't/can't move. But then physical symptoms show up a lot in my dreams. Just last night, I dreamed I was sick, when in reality I just had a plugged up nostril and felt chilly from sleeping with the fan on.

Though hah, I didn't realize the mouth full of gum dream was common! Maybe that's from having a dry mouth while sleeping?
posted by yasaman at 3:21 PM on October 12, 2012

I was curious about this too, so I asked my Romanian students. None of them had ever had nightmares about their teeth. I think that one's just prominent in cultures where we are obsessed with dental care, like the U.S.
posted by chaiminda at 3:29 PM on October 12, 2012 [2 favorites]

I would argue that Western humans have many of the same anxieties and hopes, and that may be why many of us have similar dream themes. Whenever I am crazy, crazy stressed or upset, I dream about losing teeth or having my mouth full of chewing gum I can't remove because those things are in and of themselves anxious situations. My friends have the same dreams, even though we've newer talked about either situation together and only discovered our mutual dream states when I complained about a particularly bad dream and what was in it.
posted by These Birds of a Feather at 5:02 PM on October 12, 2012

Parasitic Worms
posted by sarastro at 5:06 PM on October 12, 2012

I think most common dream topics reflect culture and environment instead of physiology, although I think telegraph's hypothesis about sleep paralysis and not being able to move in a dream makes sense.

But some dream topics aren't universal, even in similar cultures or where you think someone's personal history would set them up for it. For example, a couple of siblings and both my parents actually lost some or all of their teeth (I moved out of Montreal just in time!), I had several traumatic dental visits when I was a kid, I had an uncomfortable dental visit earlier this year, and I tend to clench rather than grind my teeth, but I have never, ever dreamed about losing my teeth. I'm Canadian, not Romanian, for what that's worth.

Lots of school anxiety dreams, though. Hoo-boy.
posted by maudlin at 5:30 PM on October 12, 2012

An interesting corrolary is how schizophrenia and psychosis manifest depending on cultures. Nobody had black helicopter or alien hallucinations prior to their introduction into culture. So there are probably deep down embedded fear patterns that get "poked" during fear dreams. For example, I live in an area where tornadoes can occur rarely, and many of my anxiety/fear dreams contain tornadoes.

The teeth one might be more universal, because we all lose all our teeth at least once in our lives.
posted by gjc at 6:13 PM on October 12, 2012

For me and another family member, dreams of running and running are induced by episodes of low blood sugar. (I think the school dreams are metaphorical. But running dreams can be physiogically based, an interpretation of the higher heart rate and other symptoms associated with low blood sugar.)
posted by Michele in California

That's a good candidate, Michele in California, and the link could even be more direct than that. Glycogenolysis is one of two main ways a person raises blood sugar when it gets too low without external input, and it takes place mainly in the muscles and the liver.

And in muscles, "glycogen degradation may also be stimulated by neural signals.[2]", which raises the possibility you are having these running dreams because you are directly stimulating your muscles to produce glucose.
posted by jamjam at 6:45 PM on October 12, 2012 [3 favorites]

I did a high school paper on hypoglycemia 30 years ago. My recollection: When blood sugar drops too low, adrenaline kicks in with the purpose of releasing stored sugars from the liver. The adrenaline also incidentally does all the other things it typically does, like increasing heart rate and respiration.

Nightmares are known to be common with hypoglycemia, as are certain other somatopsychic effects, like paranoia (from constant adrenaline rushes with no apparent cause, which lead to fight or flight reactions and looking around suspiciously at other people, trying to figure out why you are in a panic). I don't recall, though, if specific types of nightmares are known to be associated with hypoglycemia. But I know my most common hypoglycemia-induced bad dream is of running from something, which is my brain's interpretation of the adrenaline rush and asdociated symptoms.
posted by Michele in California at 6:56 PM on October 12, 2012 [2 favorites]

"dreams about teeth falling out happen more often among people who grind their teeth in their sleep"

Yep, that's exactly when I have those dreams—when I'm clenching my teeth in my sleep.
posted by limeonaire at 9:13 PM on October 12, 2012

My hypothesis is the mouth-full-of-gum dream comes when your airway is getting blocked by your tongue or adenoids or whatever. And the can't-dial-the-phone dream, I think it's hard to read or understand numbers in dreams (though I'm not sure why) and the dream just takes a turn for the anxious when you realize you can't do this totally "easy" "normal" thing. (Sometimes I have "can't write down something important" or "can't read a book" dreams for, I believe, the same reason.)

As for the teeth falling out dream, I have no idea why that's universal but I sure wish it would stop happening to me.
posted by feets at 12:17 AM on October 13, 2012 [1 favorite]

I too have always vaguely assumed that the running-in-molasses-can't-yell kinds of dreams have some physiological connection to sleep paralysis. For me, they're frequently not even fear dreams: there's some fairly benign (but usually frustrating) in-dream explanation for why I can't move, or maybe there isn't even an explanation but regardless I'm not afraid. They also seem to occur for me towards the end of the dream period, when I'm on my way to waking up, which seems reasonable if there's a link to some physiological state.

The other dreams you mention seem more culturally based to me, but I think it's interesting that they're as uniform as they are. Maybe there's some kernel of them that is archetypal/innate/deep-structure or whatever, and it's selected for anxiety dreams by the particular things our culture worries about. Surely some anthropologist has done a cross-cultural survey of the frequency of different anxiety dreams?

I think it's hard to read or understand numbers in dreams

The most reliable 'tell' for me that I'm dreaming is that I can't read things— or rather, things read differently every time I read them. I've heard it claimed that this is universal, that some necessary bit of the brain isn't available or is otherwise occupied during dream states.
posted by hattifattener at 1:42 AM on October 13, 2012

Forgot to say - from the list, the only kind of dream I ever had was about teeth. As far as I remember, I never had any school dreams (neither positive nor negative) or other exam/test failing; no being unable to move/do simple tasks, nothing.
A nightmare I had as a child caused (?!) my real phobia of heights, which I didn't have at all before dreaming about being phobic (not about falling from a high place). However, I also don't have nightmares about falling/high places. So I kinda sabotage my own theory that real fears influence the kind of nightmares people have.

Culturally: Western Europe.
posted by MinusCelsius at 1:45 AM on October 13, 2012

I used to have horrible dreams about my teeth getting stuck together. And then I got an NTI mouthguard from my dentist to stop me from clenching my teeth at night and fucking up my TMJ.

I haven't had a tooth-related dream since.


And I haven't had any of the typical anxiety type dreams since I finished school.

I have a lot of WEIRD dreams these days, but they generally involve people I know, and none of the shared dream experiences I'm familiar with.

YMMV, but for me, there has always been a pretty direct link between my daily stressors and my anxiety dreams.
posted by phunniemee at 1:59 AM on October 13, 2012

Another anecdote: I do clench my teeth but never have mouth-related dreams.

On the other hand, I only have nightmares when I'm sleeping such that my hand falls asleep -- waking up from a nightmare always involves bringing the hand back to normal. I have always assumed the nightmare was my body-brain's way of waking me up in the face of a physical problem.
posted by rosa at 4:10 AM on October 13, 2012

I believe phunniemee's suggestion of Ever Dream This Man has been revealed as a hoax. There was a MeFi discussion on that as well.
posted by amoeba at 8:30 AM on October 13, 2012