Instant Genius - Intrusive thoughts – why we get them and how to cope with them

Episode Date: November 10, 2023

Do you ever find yourself going about your daily business when suddenly an unpleasant thought pops into your head? These are known as intrusive thoughts. The majority of us experience them without any ill effects. However, for some people they can be highly distressing. In this episode we catch up with Dr Scott Cairney, a senior lecturer in psychology at the University of York. He tells us all about what is going on in our brains when we have intrusive thoughts, what we can do to limit their impact on our lives and the connection they have to sleep. To take part in a short survey related to sleep and intrusive thoughts produced by Scott and his team, please click here. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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Music just as the artist intended. Visit Name, Audio, to learn more. Hello and welcome to Instant Genius, a bite-sized masterclass in podcast form. I'm Jason Goodyear, commissioning editor, a BBC Science Focus magazine. Do you ever find yourself going about your daily business when suddenly an unpleasant thought pops into your mind? These are known as intrusive thoughts.

The majority of us experience them without any ill effects. However, for some people, they can be highly distressing. In this episode, we catch up with Dr. Scott Ken. a senior lecturer in psychology at the University of York. He tells us all about what's going on in our brains when we have intrusive thoughts, what we can do to limit their impact on our lives, and the connection they have to sleep. So today we're talking about intrusive thoughts.

So first off, let's start with defining exactly what that means. So an intrusive thought can correspond to a memory of an unpleasant experience. So the best example might be if you're walking down the street and you see someone that was involved in an unpleasant experience from your past, and that might bring back intrusive thoughts and unwanted images or ideas about the past, and along with that, the various feelings of emotional arousal that come with those thoughts. So this is something that's really interesting about intrusive thoughts, because people are often reminded about things that they would rather forget,

and that brings to consciousness these thoughts of unpleasant past experiences. but along with that, they also experience these negative feelings of emotional effect and these aberrant and unwanted emotional responses. So it's almost like, you know, you're being sort of briefly taken back to the experience that gave rise to the memory that's underpinning that unwanted thought. So I'm sure that a lot of people are listening to this will think, oh, you know, I've experienced that before. So how common are intrusive thoughts? Intrusive thoughts are very common. I think the vast majority of people experience them fairly often.

You know, you can, this is by their nature. Intrusive thoughts occur without warning, but often in response to reminders that we're not expecting to encounter. So the example I gave before is, you know, coming across someone from our past, these are often very powerful reminders, but it doesn't have to be something we see. It can be something that we smell. It can be something that we hear. The smells are very interesting, actually, because they're very powerful retrieval

cues and they can, you know, very quickly take. you back to a time from your past. And often those times from your past can be quite unpleasant. And as I said, bring back all of that emotion. So intrusive thoughts are very common. People experience them all the time. And we learn to control them and adapt our memories around them and engage in different strategies to deal with them. The interesting thing about them is that for most people, intrusive thoughts can be quite fleeting and, you know, just a sort of minor inconvenience or an annoyance, but for people with debilitating mental health conditions or psychiatric mood disorders, such as anxiety and depression or post-traumatic stress disorder, intrusive thoughts can be very

persistent, can be very distressing, and as a result, it can lead to this sort of vicious cycle whereby people end up with quite a negative bias in their thinking of the past, and that also can then project onto their expectations of the future. So what do we know about what's going on in our brains when this happens, you know, and is there, because it's quite a strange thing. Is there any sort of evolutionary purpose that they serve or something like that? So it's a very interesting question, actually, and something that I'm really interested in in terms of what's going on in our brains that gives rise to these thoughts. And one way that we can think about it is that intrusive thoughts are a consequence or an

unwanted consequence of the way that our memories work. So when we see retrieval cues that engages brain regions that underpin memory. memory, and that gives rise to our experience of a memory. So when I say retrieval cue, you know, I'm just talking about a reminder that will link to a memory and engage that part of the brain known as the hippocampus, which will bring that memory to our consciousness. And the hippocampus essentially just sort of pulls all of the different parts of the memory into our consciousness so we can experience it. But unfortunately, you know, we can't really decide when we want our hippocampus to do that and when we don't, certainly not in terms of

the way that we respond automatically to retrieval cues in the environment. So intrusive thoughts can be thought of as an unintended consequence or potentially a negative consequence of the way that our memory systems are working in our brain. But what's really interesting, though, is that we can then engage other systems within our brain to respond to those unwanted consequences of the way that our memories work. And there's been a lot of work in recent years to try and understand the conditions with which those systems are engaged and the circumstances in which they're most effective. So one very clear example is a process whereby people will directly and consciously suppress those memories. So they'll sort of push them out of their mind. You can, you know, sort of when you hear

people talk about this idea of blocking something out, you can actively try and cancel or stop that treable process. And that stopping of retrieval is reliant on a brain known as the right dorsalateral prefrontal cortex or the RDRPFC for short. And what that essentially does is that it responds to this unwanted retrieval within our hippocampus and essentially puts the brakes on the retrieval episode. So you can kind of think of it registering that there's a unwanted memory operation going on and hitting the brakes and pushing that memory out of our consciousness. And what's really interesting about that is that that's an adaptive process so that when you engage these control mechanisms to put the brakes on our memories, that actually weakens the memory so that it's less likely to be intrusive in the

future. So it's an adaptive process to respond to this unwanted memory operation that occurs in the hippocampus. And we've seen that both in behavioral data and also in neuroimaging data, in that the more people engage in this reactive suppression of unwanted memories, the greater the extent of their adaptive forgetting for those memories in the future and the less likely that those memories are to lead to intrusive thoughts. And then interestingly, coming back to mental health conditions, such as anxiety, depression, and post-traumatic stress disorder, we've also seen that people who experience these conditions seem to show some level of impairment in those mechanisms, which might provide a mechanistic explanation of why they experience

these sorts of thoughts on such a debilitating level. So some people are listening might say, well, that all sounds great, but how do these intrusive thoughts differ from just regular worrying that we all go through? Well, I think that's a great question. And again, I think from my perspective, a lot of this comes down to the way in which our brains are attuned to deal and respond to these thoughts. So it comes back to the question before about how common intrusive thoughts are. And for the vast majority of people, these are fleeting annoyances, and we learn how to respond to them and how to adapt to them in the ways that are most effective for us. you know, as a brief aside, there's also a lot of work showing that different strategies for coping with intrusive thoughts have, you know, different levels of effectiveness, and some can be thought

of as adaptive and others as maladaptive. But essentially, what differs these intrusive thoughts from just fleeting worries is that we have fleeting worries and, you know, every day and we can sort of deal with them, you know, we can address them in our minds and think about how we're going to take steps to manage those worries. We can positively reappraise those worries. We can positively re-appraise those worries and think that, you know, actually maybe this might be a good thing, or we can directly suppress them, you know, using the strategy that I talked about before. But it seems that those adaptive strategies to overcome these worries may be impaired or, you know, to some degree disrupted in certain people. And this can lead to a dominance of these intrusive thoughts,

such that they become more persistent and more distressing so that, you know, for the vast majority of people, while we're just fleetingly dealing with an annoyance or an unwanted worry, other people are experiencing this on a very persistent and debilitating way. And this also just corresponds to when you, you know, most of the time, if we just have a worry or concern, we can deal with it in a short amount of time or we can talk to a friend or a family member about it and come with a resolution. But sometimes we have very serious worries that are a lot harder to forget. about or address and, you know, that can lead to more ruminative behaviours that can then, you know,

themselves lead to further problems. So I think it's, you know, all about sort of considering the nature of the worries that people have, but also the way in which their brains and their psychology is adapted to responding to them. So from some things that I've read about these sort of spontaneous intrusive thoughts, like often the content seems to be quite disturbing, like violent or sexual in nature. Is there anything linked to that or is that just because of the fact that it is a disturbing thought within itself? I think the nature of intrusive thoughts, something to be said about their nature is that they're incredibly diverse. People experience all sorts of, all sorts of thoughts related to the past, to the future or even imaginings about certain scenarios from

the past and how they might have played out in different ways. So I think in terms of the content of them, it's quite difficult to actually understand why people have thoughts with differing degrees of content or different themes. But what we can say with a fairly reasonable degree of certainty is that there are underlying general mechanisms that contribute to the emergence of those thoughts and that there are also mechanisms within our brain that we can engage to to respond to them. But again, I think this comes back to your previous question about just how they differ from, you know, just everyday worries is that if someone is experiencing, you know, very

vivid and distressing thoughts about their past or things that they're imagining about the future, you know, they're very difficult for people to address and deal with and the sorts of brain systems that we might normally engage just to suppress an unwanted, memory about, you know, seeing someone at the pub that we'd have rather not seen, they might not be sufficient to override the sorts of worries that might, you know, correspond to some of the scenarios that you mentioned before. Yeah, so you mentioned something interesting there that I like to pick up on in imagining things. So is there any sort of relationship between intrusive thoughts and, I guess, delusions?

Hmm, so that's a fascinating question. It's something I've not thought about before, actually. So I think a good place to start with that question is to say that our ability to imagine the future and to simulate how our futures might play out in different situations actually relies on memory systems. What we do is we take our memories from the past and we recombine them in a way that allows us to simulate the future. So as I mentioned, we have the hippocampus that's involved in retreating our memories from the past and bringing those to consciousness. But we also have an area of the brain called the ventrometrial prefrontal cortex, and that's involved in recombining these hippocampal memory representations into novel perspective and in a novel simulated environment

so that we can imagine ourselves in the future. The point on delusions is really interesting, because it's possible that there is a breakdown of these systems whereby people are pulling things from memory that are potentially false, that are potentially not real or distorted memories of the past, and or these prefrontal regions that are involved in recombining these events from the past are also impaired and might lead to a deluded imagination about how the future may play out, or indeed delusional ideas about someone's past or someone's present being.

And this also feeds into the negative bias that people can experience if they're having a number, of unpleasant intrusive thoughts about the past or unpleasant thoughts about the future is that, you know, that negative bias and that sort of unpleasant sort of context with which they often find their consciousness can then have an impact generally on the way in which they see the world. So I think it's a really fascinating question about, you know, how a breakdown in these processes could lead to delusional ways of thinking. Ambition comes in all shapes and sizes. At First Citizens Bank, we roll with your goals because we're built for what you're building.

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name boutique. Visit focal powered by name.com for more information. Yeah, so you've sort of touched on this already, but obviously these types of intrusive thoughts are more distressing for some people than others. So you mentioned PTSD, anxiety, depression. I think the big one that people will think about is obsessive-compulsive disorder. So first off, I think it's a very misunderstood condition. Can you explain what that is and how intrusive thoughts play a role in this condition? Obsessive-compulsive disorder is a psychological condition whereby people are often consumed by thoughts related to different components of their life or different experiences that they find themselves in that can be very debilitating and overwhelming. And it can also describe instances in which

people engage in repetitive behaviors in a way to sort of satisfy this underlying, underlying feeling or need to feel fulfilled in a certain way to reach a sort of certain degree of fulfillment about an activity that they're engaging in. So when we think of obsessive compulsive disorder and it's linked to intrusive thoughts, there's some very interesting overlaps in the nature of obsessive thoughts and often people can feel consumed about obsessions that they may have about a particular environment and they find themselves in and find themselves having these rather distressing and often really quite unpleasant and debilitating thoughts about situations that they might find themselves in.

So obsessive-compulsive disorder is certainly a psychological condition that seems to be strongly linked to a sort of disproportionately large amount of intrusive thinking and potentially a breakdown of the neural systems that are typically engaged to override those sorts of thoughts and keep our consciousness in an area that we would like it to be. So let's have a look at, like, are there any external factors that can make intrusive thoughts more prevalent or more likely to occur? So I'm thinking of things like stress. Yes, so something that I'm really interested in is sleep. One of the main things that we focus on in my research group at York is on the relationship between sleep and mental health. And something we've

known for an awful long time is that sleep problems are intimately related to mental health conditions. A number of, well, the vast majority of mental health conditions to some degree have sleep problems as a related symptom. One of the questions that we're really interested in is on understanding what it is that breaks down in the brain that can link sleep problems to common mental health conditions such as anxiety and depression and post-traumatic stress disorder. We've found in work that we've been doing in the past couple of years, we've demonstrated that sleep is a really important factor in our ability to control intrusive thoughts. This might provide some mechanistic insight into why sleep problems might be a risk factor for various psychological disorders. So we ran an

experiment a couple of years ago now where we had university students come into the lab and they carried out a task where they had to learn and learn various associations between faces and different scenes. So, you know, images, for example, of one image could be, you know, of a golf course, another could be of a casino, something like that. But interestingly, the scenes were emotionally negative and emotionally neutral. So the neutral ones could be like, you know, as I mentioned, a golf course or a negative scene could be an image of a riot, for example. So we overtrain people on these associations such that when they see the face, they automatically begin to engage in a retrieval process and bring that scene to consciousness.

What we did the following morning was we presented people with those faces alone, and there were two different conditions that they had to engage in while they were taking part in this experimental task. So when they saw the face, they were either told, that they had to suppress the associated memory, so push that memory out of consciousness or retrieve the associated memory. So, you know, sort of bring it into their conscious awareness. Now, what was absolutely crucial is that between those evening and morning sessions,

the university students either slept overnight in our lab or they were sleep deprived across the entire night. So we had people stay up with them and keep them awake across the entire night. And what we found the next day is that when people were sleep deprived, they did a really terrible job at stopping these unwanted memories from coming into their conscious awareness when we were instructing them to suppress. So they would attempt to suppress those unwanted memories, but they would often fail, and we would determine whether they'd fail based on a self-report on each of their attempt.

This is very interesting because it demonstrates that when people are sleep deprived, they're unable to engage in these control processes in a way that when they would, when they've slept and they're well rested. And in a follow-up study that we're hoping to publish in the near future, we're just finishing up the paper, we repeated this experiment but did it in an fMRI scan. So we could actually see what was going on in people's brains while they were attempting to suppress those unwanted memories.

So as I mentioned earlier, this very well-established neurocognitive mechanism of memory suppression, which involves right dorsalateral prefrontal cortex, which engages a sort of a stop mechanism on the hippocampus. And this has been shown several times. Now, in participants that had slept, when they were engaging in memory suppression, when we were giving them these reminders,

these face cues and telling them to suppress the associated scenes, they were engaging the right dorsetal prefrontal cortex. It was lighting up and we could see that part of the brain coming online to do its job of stopping the retrieval operations. And then interestingly, we also saw a reduction of activity within the memory center of the brain, the hippocampus. So the brain was doing its job to support that suppression process. It was engaging right door, slatural prefrontal cortex to put the brakes on the hippocampus. When people were sleep deprived, we saw the complete opposite.

So now, when they were engaging in memory suppression, we saw this relative to people that had slept. We saw this reduction in activity in right, dorsal lateral prefrontal. cortex, so showing that they were unable to engage that area of the brain effectively. But then what was really interesting is there was also then an increase of activity within the hippocampus relative to the people that had gone to sleep. So what this is demonstrating is essentially the hippocampus was just free to do what it wanted. It didn't have this typical prefrontal control region putting the brakes on it. So these memories were just coming back online.

And that provides some insight at a brain level into what may be going on when people are experiencing intrusive thoughts in a highly emotional and debilitating way, when they're not sleeping well, is that the neural systems that are in place to help us deal and control with those memories are just not working effectively. And then when we consider the fact that people with anxiety, with depression, with post-traumatic stress disorder, often have very serious sleep complaints or co-occurring insomnia, this can tell us why, you know, this might give us some insight into, you know, how that, that sleep problem can give rise to intrusive and unwanted thoughts that might eventually lead into a mental health condition, or it might be related

to the persistence of that mental health condition. If we're not able to treat the sleep that these people have, then it's going to have a drastic and, you know, market impact on their ability to overcome these thoughts and overcome their symptoms of the disorder that they're experiencing. So sleep is, you know, we keep hearing, you know, all the time, it's a very hot topic at the moment, how important sleep is for our mental health. And the work that we're doing is, is telling us on a, on a brain level of why that is. And, you know, that can then potentially, these mechanisms can then potentially be a target for psychological therapies or other treatments to help people overcome these problems. Yeah, so you mentioned treatments there. That was something that I'd like to talk about next.

So how do we go about treating someone who's struggling from distressing intrusive thoughts? There are a number of treatments that are already out there to a number of psychological therapies that can help people to approach intrusive thoughts in a way that re-appraises them. So a number of psychological therapies for different psychiatric mood disorders, for example, will focus on reappraising negative ways of thinking to help people approach the environment around them, be it their future environment or their ways of thinking about the past in a more adaptive manner. Interestingly, we've seen that sleep also seems to play a role in people's ability to reappraise their past experiences or their interpretations of the future and the way in which they think.

So it seems that targeting sleep is something that would be very important for the success of these treatments that people often undergo to try and overcome their intrusive memories. And what's very interesting is that, you know, often in environments where people are undergoing intensive treatment for mental health conditions in secure psychiatric units, for example, people often are, you know, in situations that can impact on their sleep. So, you know, they have, there's lots of other fellow patients around them. There's the staff that are, you know, working night shifts as well, which can have an impact

on their sleep and impact on their on their recovery. So I believe, I firmly believe that one way to treat intrusive thoughts and disorders that are characterized by those sorts of thoughts is to focus firmly on sleep, not just because sleep is important for the mechanisms that allow us to control these thoughts in our brain, but also because sleep is important to allow people to benefit from the psychological therapies that can also be used to help people think about these sorts of events in a different way. Thank you for listening to this episode of Instant Genius, brought to you from the team behind BBC Science Focus.

That was Dr Scott Kearney, a senior lecturer in psychology at the University of York. To take part in a short survey related to sleep and intrusive thoughts produced by Scott and his team, please click on the link in the episode description. The current issue of BBC Science Focus magazine is out now. Pick up a copy wherever you buy your favourite magazines. or download us on your preferred app store. You can also find us online at sciencefocus.com. This podcast is sponsored by Name, Audio and Focal.

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