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Go to CuriosityStream.com/Psych to learn more. [ ♪INTRO ]. When you're dreaming, things normally don't feel all that tangible.

Like, you can pick up your phone or a trophy or a puppy-sized elephant, and it won't feel as solid as those things would in the real world. But then, when you wake up and grab your phone to turn off the alarm, everything goes back to normal. There's nothing to suggest your phone isn't real, or that the hands you use to touch it don't belong to you.

That is... usually. Sometimes, even when we're awake, our brains decide it might be in our best interest for our environment, or even our bodies, to just… not feel real for a while. And this isn't a rare thing, either.

It's actually a super common experience. But when it sticks around for longer than it should, it can merit its own diagnosis. This condition is called depersonalization-derealization disorder, and it's sometimes abbreviated as DDD.

According to the DSM-5, which psychologists use to diagnose disorders, the name of this condition is pretty descriptive. DDD is defined by persistent or frequent episodes of depersonalization and/or derealization. Depersonalization is the feeling that your body, thoughts, sensations, or actions aren't your own, or aren't even real — even though you logically know they are.

Derealization is a similar feeling, but it's about your surroundings and the things in them. Some people say that experiencing these things is like having a glass wall between themselves and the world. For others, everything might feel far away and dream-like, or it might feel like their head is stuffed with cotton.

Regardless of what they feel like, though, these symptoms aren't actually uncommon. Experiences of depersonalization or derealization are thought to be the third most common mental health symptom after anxiety and low mood, and they occur equally in men and women. But when these experiences don't go away, that's where DDD comes in.

And that is much rarer: It's estimated to occur in only around 1-2% of people. Unfortunately, the factors that lead to its development and trigger the symptoms are still fairly unknown. It's often associated with cannabis usage, but there are plenty of purely psychological causes, too.

For example, some research has suggested that childhood trauma could play a role in developing. DDD later in life, especially when that trauma involves emotional mistreatment. Anecdotally, many people have also reported that their symptoms are related to periods of extreme stress or anxiety.

That's led some scientists to believe that depersonalization and derealization are mechanisms the brain uses to protect the mind from potential threats. But even if they can't say what specifically triggers these episodes, they are recognizing some general patterns. Research from 2018 in the journal Consciousness and Cognition found that certain types of triggers were more likely to induce either depersonalization or derealization.

In the study, they tested 73 participants who were prone to one of these things, trying to find out if their symptoms would kick in in response to different kinds of threats. To do this, they performed something called the Implied Body-Threat Illusion task, which was a simulated blood-test procedure. In it, the researchers don't actually draw blood, but they used fake needles and special effect blood to make it look like they did.

Everything was pretty realistic, because the point was to see how participants responded physiologically to threats. First, participants had this procedure done to them alone. Then, they witnessed it being performed on a person sitting next to them.

The whole time, the researchers were measuring their temperature and how their skin conducted electricity, also called skin conductance. That might sound like a weird thing to test, but it's partly because being threatened makes us sweat, and water is a good conductor. When the scientists looked at the data, they found that those predisposed to depersonalization showed normal skin conductance when someone else got a blood test, but decreased conductance when someone was about to perform a test on them.

That likely means that their brains were making everything seem farther away and less real — and their dampened physiological response showed it. On the flip side, in those prone to derealization, their threat response was only dampened when they saw someone else experience the blood test. Even though the threat wasn't aimed at them, it still existed, so it could have had psychological consequences.

And to shield them from that fallout, their brains chose to make their environment seem less real. These findings support what's known as the threshold model for these experiences. It suggests that when we detect a threat, the regions in our brain responsible for emotional processing — called the frontolimbic regions — may suppress our stress response to it.

As a result, the stress is more dull, and easier to handle. And in those that are prone to depersonalization and derealization, the threshold for this response is thought to be way lower. So their brains might think things like talking to a cashier are enough of a threat to cause those numb and unreal sensations.

Sometimes, these symptoms can be managed with psychotherapy. But in many cases, the usual treatments aren't actually effective, so scientists have been looking into other techniques. One promising method is called repeated transcranial magnetic stimulation, or rTMS, and it uses powerful magnets to disrupt the electrical activity of small brain areas.

Specifically, using rTMS on a brain region called the right temporoparietal junction seems to help symptoms — at least, it did in a small study of 12 DDD patients. But the studies' authors do admit that the study is pretty underpowered, and that they still can't rule out placebo effects. So other authors are using rTMS to target different brain areas.

Another promising candidate is an area involved in the brain's executive control system called the right ventrolateral prefrontal cortex. A study from 2016 showed that using rTMS on this area improved symptoms in six of seven patients after 20 sessions, with few side effects reported. Scientists think that damping down its activity bumps up that threat threshold we mentioned earlier, stopping symptoms from being triggered so easily.

But again, we don't have larger studies to back this up, so psychologists will need to keep working. Sometimes, it can feel frustrating when scientists don't totally understand a phenomenon or how to treat it — especially with something like DDD. But the truth is, each small experiment does get us closer to understanding what's going on.

Someday, maybe we'll understand all of the brain's secrets. And if we do, it will be because of research like this. If you want to learn more about how scientists are tackling some of the biggest challenges in psychology, you might like CuriosityStream.

It's a subscription streaming service that offers over 2000 documentaries and nonfiction titles, including plenty about psychology. There's a whole series called Curious

Minds: Brain Health that, well, talks about brain health. There are episodes on Alzheimer's, depression, and a handful of other disease psychologists and doctors are working hard to understand. All of the episodes are pretty short, too, which means they're a great overview if you just want to understand the gist of a topic. You can get unlimited access to CuriosityStream starting at $2.99 a month.

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