How The Brain Responds To Threat When Experiencing Intrusive Thoughts

People with OCD struggle with painful, intrusive thoughts. As a result, their brains get confused, leaving them feeling uncertain about their moral values. 

For example, consider Dave, who experiences conflict when he gets paedophile-intrusive thoughts (POCD) and feels sudden movement down there. He’s instantly terrified he’s a threat to children. But he needn’t be. And that’s because the sensation is a reflex. His nervous system triggers an involuntary response after being subjected to internal or external stimuli, such as thinking about or being around kids.

Have you ever noticed twitching in some anxious people, like their cheeks and eye twitching? It does this when a muscle, or group of muscles, moves without conscious thought or action. In that case, it’s automatic and not the person’s fault. So you can imagine how Dave experiences unconscious movement down there when he’s anxious.

Amygdala Activation

First, the brain’s amygdala is constantly alert, scanning for danger to protect us and others from threatening situations. So when it detects that Dave could be attracted to kids, it fires up. In other words, his amygdala forewarns him to be careful through feelings, not words.

Of course, the amygdala doesn’t recognise that intrusive thoughts and sensations are false alarms. It thinks they’re real, which is why Dave gets the urge to avoid triggering situations. His avoidance is a compulsion associated with a fight response and reduces his anxiety momentarily. Other times, he escapes the problem related to a flight response. In other words, he flees the triggering scene to prevent the thoughts from turning to reality and, again, to reduce anxiety.

So what can Dave do?

Even though his anxiety becomes high, Dave can learn to calm his amygdala and show that it does not need to arouse a fight or flight response. First, deep breathing exercises are good because the amygdala responds to calming activities. Then, when it’s calmer, Dave’s cortex, the thinking area of his brain, can step in and help him reason with common sense. Unfortunately, it can’t help him do this when the amygdala is going full force because it blocks the cortex from acting with a rational mind. So when it’s quieter, the cortex gets the chance to signal that the POCD thoughts are false and not to worry.

Breaking The Connection

But it doesn’t end there. Dave’s therapist reinforces that he must do practical exercises to change the amygdala’s responses. These actions are the opposite of compulsions. It means facing the thoughts that the amygdala got wrong and not avoiding or fleeing the feared situations. That way, Dave can break the connection that makes him think rituals prevent a terrible thing from happening. These exercises are known as exposure and response prevention (ERP), an evidence-based treatment for OCD.

The Freeze Response

Dave agrees that ERP could be helpful but worries about the times when he feels immobilised. For example, he feels numb when children are around him and appears to stare at them. And so he thinks it must mean he’s secretly attracted to them. However, he learns that feeling immobilised is another fear reaction, as well as fight and flight. This time it’s a freeze response.

Dave also learns that his amygdala will settle down by itself within 15-30 minutes and usually no longer than an hour. That being so, he figures he can tolerate the fight, flight or freeze response and wait for his cortex to free up and suggest rational ideas for managing his situation. In other words, he gets the opportunity to influence what happens next, for example, by using response prevention in ERP.


Therefore, Dave learns that his amygdala needs to be activated for ERP to work. In other words, it involves a habituation process in which Dave must face his fears in graded steps, resist compulsions and expect increased anxiety. So, suppose he strolls through a play park. In that case, he will allow anxiety to rise, resist avoidance and wait for the anxiety to diminish. If Dave experiences a freeze response, he knows to breathe, wait it out, and not analyse his thoughts, which is a mental compulsion. As a result of ERP, he builds distress tolerance, becoming less sensitised to his irrational fears over time. Again, his amygdala gradually becomes less active in triggering situations.

Recall that since the amygdala doesn’t know the difference between facing a real fear or obsessive fear is why challenging fearful situations in ERP fire it up, thus leading to habituation. Of course, Dave does visual exposures, too. But, again, his amygdala doesn’t know what he conjures up in his mind isn’t real, so it becomes activated, which is the idea. Subsequently, he becomes less sensitised to POCD.


In short, intrusive thoughts and sensations come from the brain automatically. As a result, the amygdala activates a fight, flight or freeze response. Then, a person will assign meaning to them and develop an obsession. Breathing exercises soothe the amygdala. Finally, ERP makes it less active, leading to habituation.

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