This is one of those topics that doesn’t really get a proper look in until you’ve been in the field a long time. I remember, during my undergraduate degree in psychology, we studied perception in a fairly straightforward way—illusions, visual processing, that sort of thing. Then, later during my professional training, most of the focus was on cognitive behavioural therapy, where we were taught to help people challenge distorted thoughts.
But it’s only with 20 years of experience behind me that I can really see how all of that connects—how OCD doesn’t just distort thoughts, but perception itself. And not in a dramatic or psychotic way. In a subtle, unnerving way. Things feel a bit off. You can’t quite trust what you saw, or what you remember. It’s real enough to unsettle you but vague enough to keep you in doubt.
It’s Not Just Thoughts
I can’t count the number of times someone’s said to me, “I saw something, but I don’t know if I really saw it,” or “I think I said something awful, but I have no memory of it.” The first time I heard this, I was still in training and sitting in on a case consultation. I remember wondering, is this OCD? Or is it something else?
It’s OCD. Just not the textbook version.
People often become hyper-aware of small sensory details—sounds, glances, flickers of light or facial expressions—and their brains flag them as important. But instead of trusting that these are just normal bits of life, OCD gets involved. “What if that glance meant something?” “What if that flicker was something inappropriate?”
And here’s the tricky bit: the more attention you pay, the less certain you feel. It’s like when you stare at a word for too long and it stops looking like a real word. That’s perception distortion—not psychosis, not hallucination, but a side-effect of obsessive attention.
How It Works (with the benefit of hindsight)
Back when I was doing my doctoral training, I heard a lecturer mention sensory gating—your brain’s ability to filter out things that don’t matter. At the time, I nodded and moved on. But years later, in my own clients, I saw what it looked like when that filter wasn’t working properly.
People would come in describing how the world felt too loud, too sharp, or just not right. And once I linked that to OCD’s constant scanning for threat, it made more sense. If your brain is stuck in detection mode, of course the background noise gets turned up.
One talk I attended in Belfast years ago compared this to having a faulty smoke alarm—it goes off at burnt toast, not fire. That image stuck with me. It’s a good way of explaining how OCD hijacks normal perception.
Memory and Meaning
This is where things get particularly unfair. People with OCD often don’t trust their memory. I’ve written more about this in my false memory OCD article, where I go into detail about why this happens and what can help. They’ll say, “I feel like I did something wrong, but I can’t remember it.”
That’s not because they’ve forgotten. It’s because anxiety interferes with how memory is formed in the first place. I came across this in research during my master’s—a study linking elevated cortisol to impaired autobiographical memory. And it fits. When your nervous system is in a state of threat, you’re not storing events properly. You’re surviving them.
So then what happens? You go looking. Mentally rewinding. Trying to “feel” sure. But that sense of certainty never quite lands, because the system that should give it to you is the same one that’s been overwhelmed all along.
What Actually Helps
In practice, I don’t try to reassure people that nothing happened. That usually backfires. Instead, we work on the part that wants certainty.
That might mean exposure work, where we deliberately let the doubt hang in the air. Or psychoeducation, helping someone understand that their brain is flagging things as threats simply because it’s been trained to do so.
One client said to me, “It’s not that I know everything’s okay now—it’s that I don’t need to be 100% sure anymore.” And that’s exactly the goal. Not perfect perception. Not flawless memory. Just enough peace to get on with life.
If You’ve Felt This
If any of this sounds familiar, you’re not alone—and you’re not fragile.
This is exactly the kind of thing I cover in my course on intrusive thoughts and OCD-related uncertainty. Not in a gimmicky way. Just real-life examples, clinical experience, and ways to start pulling yourself out of the loop.
It’s taken me decades to join the dots between what we learn in theory and what we see in real life. I hope this helped you do the same.
