What Pure O actually is, and why it goes unrecognised
OCD with no visible rituals is still OCD. The compulsions are mental, which is why Pure O can run for years before anyone, including you, names it.
You have read about OCD and it did not seem to fit. You do not wash your hands until they crack. You do not check the oven forty times. There is nothing anyone could see. What there is, instead, is a thought, and hours every day spent inside your own head dealing with it.
Analysing it. Checking whether it is still there. Checking how you feel about it, and whether the feeling is the right one. Arguing with it. Testing yourself: if I imagine this, do I feel what I should feel? Replaying a moment from years ago to establish, finally, what it meant. Then doing it all again, because the answer did not hold.
This is what people call Pure O, and I want to explain what it is, because the name is slightly misleading and the misleading part is what keeps people from getting help.
The O and the C
OCD has two parts. Obsessions are the intrusive thoughts, images or urges that arrive uninvited and cause distress. Compulsions are what you do to make the distress go away. In the familiar picture, the compulsions are physical: washing, checking, arranging, counting.
Pure O was named on the assumption that some people have only the obsessions, with no compulsions at all. That turns out to be wrong. The compulsions are there. They are simply mental, which means nobody can see them, including, often, the person doing them.
Rumination, mental reviewing and checking how you feel are all compulsions. So are neutralising a bad thought with a good one, saying a phrase in your head, and replaying an event to reach certainty. They do exactly what hand-washing does. They bring a moment of relief, and they teach the brain that the thought was a real threat that needed dealing with, which makes the thought come back louder.
Why it goes unrecognised
Because nothing is visible, Pure O can run for years. Partners do not notice. GPs do not see it. The person themselves often does not think of it as OCD, because they have the same picture of OCD as everyone else, and what they do does not look like that. They think of it as overthinking, or anxiety, or a sign that something is deeply wrong with them.
There is also the content. The thoughts in Pure O are often the ones people find hardest to name: harm, sexual themes, blasphemy, doubts about identity or relationships. The shame of the content keeps it secret, and the secrecy keeps it untreated.
The mechanism is the same
Pure O is OCD, and it runs on exactly the same engine as every other form of it. A thought arrives. An alarm goes off. Something is done to switch off the alarm. The relief is brief, the alarm is reinforced, the thought returns. Whether the something is washing your hands or reviewing a memory for the hundredth time makes no difference to the mechanism, and it makes no difference to the treatment.
How it is treated
The treatment is CBT with exposure and response prevention, the approach NICE recommends for OCD, adapted for thoughts rather than visible rituals. The adaptation matters, because with mental compulsions the first job is often just to see them. Most people who come to me with Pure O have never thought of their reviewing as something they are doing. It feels like something that happens to them. Learning to notice the moment a thought becomes a compulsion, the moment you start working on it, is the first step.
Then we practise not doing the work. Letting the thought be there, unanswered. Not checking how you feel about it. Not reviewing the memory. Not arguing. This is response prevention for a compulsion nobody can see, and it is uncomfortable in exactly the way response prevention always is: the urge rises, and then, if it is not obeyed, it falls.
We will not debate whether the thoughts are true. I will not offer reassurance about their content, because reassurance is just another compulsion, one that happens to involve me. What we work on is how your brain responds to the thoughts, so they can pass through the way other people's do.
Saying it out loud
I know these themes are hard to name. Many people start with the general theme and share more as trust builds, and that is fine. You will not shock me, and you will not be judged. A large part of this work is helping people say, for the first time, the thing they have been dealing with silently for years.
If you have been calling it overthinking, and it is taking hours of your day, there is more on how I treat intrusive thoughts and Pure O.