Is it really harmful to wake someone who is having a nightmare, or is this an old wives tail?

Harmful? No.

However, you generally only remember a dream if you wake up unexpectedly either in the middle of it or very soon after it is over. Otherwise, you normally won’t recall much about it if you recall it at all. So if you wake someone up in the midst of a nightmare, you will probably help ensure they remember the nightmare. If they can sleep through it, come morning they may not remember it at all.

If you’re sleeping with that person at the time, and he/she is scaring the crap out of you, by all means, you gotta wake them up.

That’s the first time i ever hear of it.

Anyway @EmpressPixie seems to make sense

I’ve heard that it’s advised not to wake someone who is sleep walking if possible because they may wake up and be so shocked that they are not where they went to sleep that yeah I guess it’s dangerous or something. But I don’t remember where I heard this, sorry.

I have had terrible dreams, and I was grateful my wife woke me. Sometimes she didn’t wake me, and I had to suffer through the whole thing. It’s better to be woken.

The problem with your comment, @filmfann, is that you cannot take into account times she didn’t wake you that you didn’t remember. Unless you were hooked up to a sleep machine and they were watching you.

Except that I remember bad dreams. They don’t automatically disappear. Some stay, and bother me for days after.

@filmfann: But you can’t know that you remember EVERY bad dream. You might have ten times more bad dreams than you THINK you do.

Anyway, in MY case, it’s harmful for YOU if you wake me from a nightmare. I’m likely to lash out physically. I wake up poorly and sometimes it takes me quite a while to realize what was going on was a dream and I’m not sleeping anymore.

It tell you…it’s REALLY harmful to wake someone up who is having a nightmare and you happen to be wearing a Freddie Krueger mask.

I think the original old wive’s tale suggests that you should never wake a person while sleepwalking, which is incorrect.

Never waking up a sleepwalker seems to me likely to be a good thing to say if you want to have fun seeing what they do, like in a spooky mystery story, which I expect is where many of us have heard it, as kids.

I’m an old wive, but this is no tale of mine. I always awaken my husband when he’s having a nightmare. They’re typically both noisy and vigorous, fighting or running away from the bad guys. I wake him in self-defense and for the sake of peace and quiet.

I say always wake someone that is having a nightmare.

I think it’s harmful to wake someone having night terrors, but probably not regular nightmares.

I’d always heard the “logic” of it (inasmuch as it can be called logic) is that the shock of being pulled out of one stressful situation into another unexpected (and probably stressful situation, being woken up out of a sound sleep by another person can be very off-putting) could result in too much stress/adrenaline and could give someone a heart attack. Of course ANYTHING “could” happen, even death by anal penetrating chair.

@ubersiren In the case of night terrors, those occur at a particularly deep level of sleep so it is not physically possible to wake someone up from a night terror. If they can be woken up from it, it’s not a true night terror.

In light of @The_Compassionate_Heretic‘s answer, I am reminded that in the case of sleep paralysis, it is always best to disturb the individual experiencing it. It is horrific.

@ubersiren and @The_Compassionate_Heretic My son has night terrors, there is no waking him. As much as you want to wake them to help them, you can’t. It’s terrible to see him have these, he has a look of sheer fear on his face. We’ve found him huddled up in the corner of his room, screaming for his life, before. That’s just one example. Thankfully, as he has gotten older, they have started to slow down.

@cak : Thanks for the explanation. I’ve heard awful things about them. I’m so sorry you have to go through that.

Yeah, it’s sleepwalkers that you aren’t supposed to wake up, and that is because they could collapse and hurt themselves.