Obsessive compulsive disorder - OCD treatment and therapy from NOCD

What Causes Intrusive Thoughts?

By Cody Abramson

Mar 23, 20239 min read minute read

Reviewed byPatrick McGrath, PhD

Intrusive thoughts

While intrusive thoughts are one of the hallmark features of OCD, the truth is that we all experience distressing mental intrusions from time to time. Whether they’re about one’s sexuality, religious beliefs, or even an embarrassing memory, these uncomfortable mental states are an inevitable part of human life.

But why are they so common? What explains why we have them at all, and is there anything we can do to get rid of them? We spoke with Dr. Patrick McGrath, chief clinical officer at NOCD, to learn more. 

What are intrusive thoughts?

Intrusive thoughts, images, and urges are mental experiences that (i) are unpleasant or distressing, (ii) happen against one’s will, and (iii) do not align with your true feelings or values. 

Intrusive thoughts can be about a variety of topics and themes. Some examples include:

  • Contamination: What if that handrail I touched was contaminated with a deadly disease?
  • Harm: What if I veered into oncoming traffic right now?
  • Existential Topics: What if life has no purpose?
  • Relationships: What if I don’t really care about my family members?
  • Religion: What if I’ve lost my religious faith?
  • False Memories: What if I’ve done something terrible but forgotten about it?

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Are intrusive thoughts caused by anything?

Intrusive thoughts seem to pop into our minds out of nowhere, often with no apparent trigger or cause. While there is an element of randomness about intrusive thoughts, there are some reasons and explanations for why we have them in general, as well as why our intrusive thoughts focus on the topics that they do.  

Why do we have intrusive thoughts at all?

As Dr. McGrath notes, a major part of the answer is that “no one’s in total control of everything that runs through their head.” If we were entirely in control of our thoughts, we would never choose to experience intrusive thoughts, but we aren’t. 

But why would the parts of our brain that we can’t control show us intrusive images or give us intrusive urges? Dr. McGrath argues that intrusive thoughts might result from a broader biological mechanism that aims to keep us safe and prepared for bad outcomes. “We need to think about potentially bad things because we need to prepare. In some cases, imagining bad possibilities allows us to figure out how to respond to those outcomes.” For some mental health conditions, though, this system doesn’t function properly and is no longer helping with safety or preparation. “That’s one of the lies of OCD,” shares Dr. McGrath. “It says, ‘I’m going to have you think about this constantly so that you’re already prepared for it. So if it’s always at the top of your mind, you’ll never be surprised.’ This occurs in PTSD as well—you were harmed once before, so keep it at the top of your mind to never be caught off guard by that thing again.” In these cases, the intrusive thoughts go beyond serving a protective purpose and can actually interfere in our lives in a major way.

Why do we experience the intrusive thoughts that we do?

Why does one person have intrusive thoughts about harm while another focuses on sexuality or contamination? There are several potential reasons.

One might be that you simply had a bad experience with something you encountered in your environment. Dr. McGrath shares a personal experience:

When I was four years old, my mom ate some coleslaw, and I got very sick and vomited several times. The real cause was strep throat, but I didn’t know it then. I just associated coleslaw with vomiting. I would look at coleslaw and get physically ill.  Just looking at it, thinking about eating it, or even smelling it would cause all kinds of intrusive and unpleasant experiences. It was just disgusting to me, and I didn’t eat coleslaw for 35 years.

In this particular case, Dr. McGrath’s negative experience with coleslaw and strep throat meant that he was wired to have intrusive experiences whenever he thought about, saw, or smelled coleslaw. He explains: “Food aversion can be very powerful in us and makes evolutionary sense—if you eat something and it makes you sick, never eat it again.” 

Intrusive thoughts tend to be about outcomes people don’t want to occur or things they don’t want to be true of themselves. For example, someone may have an intrusive thought about being sexually attracted to a family member because they believe it would be morally wrong to have those feelings. Similarly, they may focus on the possibility of being a narcissist because they think it’s bad to be one. As Dr. McGrath notes, anxiety and intrusive thoughts are about picking the worst-case scenarios. These will be different for each individual based on their experiences, values, fears, hopes, and aspirations. 

What makes it more likely you’ll experience intrusive thoughts?

There are a variety of factors that can make it more likely to experience intrusive thoughts. These include:

  • Having OCD: OCD is characterized by frequent and distressing intrusive thoughts. So, if you have OCD, you may have them more frequently.
  • Being diagnosed with an anxiety disorder: OCD used to be listed as an anxiety disorder, but was reclassified in its own category: OCD and Related Disorders. In anxiety disorders, such as social anxiety disorder, one may have many intrusive thoughts about having to interact with people.
  • Attributing a lot of meaning to intrusive thoughts: The more you pay attention to intrusive thoughts and believe that they say something bad about you, the more likely you are to experience them.
  • Having experienced a stressful event: Intrusive thoughts can often come in response to negative experiences.

Can trauma or stress contribute to increased intrusive thoughts?

Whether you have a mental health condition or not, trauma or stress can increase the chances that you’ll have more intrusive thoughts in the future. For example, trauma can lead to PTSD, which, among other things, is characterized by intrusive experiences like flashbacks and nightmares. 

Stress can also precede and exacerbate the symptoms of OCD, including intrusive thoughts. For example, one study found that compared to control groups, individuals with OCD were much more likely to report a stressful life event in the six months prior to the onset of their OCD. Other research has found that periods of high stress are associated with more severe OCD symptoms

More generally, intrusive thoughts thrive on negative experiences. Any particularly stressful event can make intrusive thoughts more frequent and distressing. 

Are Intrusive Thoughts a Sign of OCD?

Intrusive thoughts can be a sign of OCD, but they don’t have to be. Everyone has intrusive thoughts, and most of the time, they are nothing to worry about. One study found that 94 percent of participants admit to experiencing intrusive thoughts, likely an underestimate given that many people are reluctant to admit to certain taboo or uncomfortable thoughts. For example, some people may not be open to acknowledging that they’ve had the intrusive thought, “What if I were to somehow hurt my child?” even if it was a common thought for them.

With that said, intrusive thoughts are one of the hallmark features of OCD, so in many instances they can be a sign that one has the condition. Here‘s what to look out for:

1: You believe intrusive thoughts have a special meaning or significance

While it’s normal to feel a little unsettled by intrusive thoughts, getting stuck on what they might mean or say about you can suggest that they’re a sign of something more. 

2: You perform compulsions

Intrusive thoughts don’t typically result in any kind of behavior done to reduce the anxiety they cause or prevent some bad event associated with them from occurring. People with OCD, however, are likely to respond to obsessions by performing compulsions. So if you find yourself performing physical or mental behaviors to neutralize the anxiety that comes from intrusive thoughts, this may be a symptom of OCD.

3: Intrusive thoughts interfere with your day-to-day life

As with many mental health conditions, part of what determines whether there is a problem is whether you’re having trouble living your life the way you want. If your intrusive thoughts negatively impact your ability to function in the areas of life you care about, they may suggest you have OCD. 

Do intrusive thoughts “mean” anything?

After experiencing a distressing image or thought, it’s natural to wonder whether there is any significance to it. For example, you may be worried that it says something about who you truly are or what you really think. 

As Dr. McGrath notes, whether an intrusive thought means something to a particular individual is highly subjective and a matter of perspective. “I work with people who believe their thoughts have a ton of meaning, even though we don’t have any evidence that that’s actually the case,” he says. “As the therapist, I could have the exact same thought they have and not be bothered by it whatsoever and not see the thoughts as meaning anything at all. If the thoughts in and of themselves had significance or meaning, it wouldn’t matter who experienced them.” 

So, different individuals can attribute different meanings to the same intrusive thoughts. But setting that aside, we might wonder if, in any objective sense, intrusive thoughts can be evidence of anything, and in particular, what one truly believes or wants. 

They can, but not in the sense that individuals with OCD are worried about. For example, having the intrusive thought “What if I physically hurt my friend?” doesn’t mean you actually want to do that or are at risk of doing it. However, it probably indicates that you believe that hurting your friend would be a horrible thing to do. It might also suggest that you feel that simply thinking about hurting your friend is morally as wrong as actually hurting them. This is called thought-action-fusion, or TAF, and it’s very common among individuals with OCD.

As noted above, experiencing intrusive thoughts might mean something insofar as these thoughts can be a sign of mental health conditions like OCD, so it’s important to be mindful of what one’s reactions to their thoughts are, rather than the content of the thoughts themselves. 

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Is it possible to stop intrusive thoughts?

No, it is not possible to stop having intrusive thoughts altogether and forever. However, you can reduce their frequency or make them less distressing. Here are a few tips.

1: Don’t try to figure out what they mean

While it can be helpful to understand the nature of intrusive thoughts, agonizing over why you had a particular thought or whether it says something bad about you will only make things worse.

2: Don’t try to push them away

Trying not to think about any thought makes it more likely that you’ll think about it. This is often called the “pink elephant” effect—try not to think of a pink elephant right now, and you’ll understand why. Instead of resisting intrusive thoughts, simply allow them to exist when they do.

3: Don’t let intrusive thoughts be an obstacle

Your intrusive thoughts might make you think you need to avoid certain situations. For example, if you have intrusive thoughts about contamination, you may feel you need to avoid social gatherings that you otherwise would have enjoyed. This will only cause intrusive thoughts to grow more powerful. Instead of avoiding them, confront your intrusive thoughts head-on and learn that they don’t mean what you think they do. 

4: See a mental health professional for ERP

If you find you can’t manage your intrusive thoughts on your own, it’s worth seeing a mental health professional who can walk you through evidence-based solutions. When it comes to tackling intrusive thoughts, exposure and response prevention (ERP) therapy is the gold standard. 

In ERP, people are exposed to whatever triggers their obsessions or intrusive thoughts without engaging in their typical safety-seeking behaviors, like avoidance, reassurance seeking, distraction, substance use, or compulsions. Over time, patients learn to sit with uncertainty and discomfort, their intrusive thoughts become less frequent and distressing, and the urge to complete compulsions subsides.

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