OCD was reclassified out of the anxiety disorders in DSM-5, and the reason is practical rather than academic. The standard tools for anxiety — weighing evidence, testing predictions, seeking reassurance, relaxation — are either useless or actively harmful in OCD.
The three tests
Does the thinking have a ritual structure? In OCD there’s a specific act — visible or entirely mental — performed according to a rule, that reliably produces relief. Check three times. Review until certain. Ask and get the exact right wording back. Generalized worry doesn’t usually have that structure.
Is it plausible or unacceptable? Anxiety worries about things that could genuinely happen and often do: the mortgage, the diagnosis, the exam. OCD attaches to the thing that would be unbearable — usually wildly improbable, and frequently something the person finds abhorrent about themselves.
Does it drift or does it demand? Worry moves from topic to topic. OCD fixes on one question and requires an answer, and the answer must be certain, which is why the question can’t close.
Why the treatments contradict
In CBT for anxiety you examine the prediction and test it against evidence. That’s effective for worry.
In OCD, examining the thought is the compulsion. Every round of weighing evidence, seeking certainty, or being reassured teaches the brain that the doubt was dangerous and that resolution is required — so it comes back louder. This is why people with undiagnosed OCD can spend years in good-quality therapy and get steadily worse.
Exposure and response prevention goes the other way: it deliberately leaves the uncertainty intact and forbids the neutralising response.
The presentation that gets missed
Someone who ruminates for hours a day about whether they’re a good person, or whether they really love their partner, or whether something they did years ago was wrong — with no visible rituals at all.
That looks exactly like overthinking with anxiety, and is described that way by most clinicians who don’t ask about mental compulsions. It’s one of the main reasons the average delay to OCD diagnosis is over a decade.
The question that separates them: is there a specific mental act you perform to make the feeling go down —reviewing, arguing, checking a memory, mentally reassuring yourself — and does it work briefly and then stop working?
Both at once
Common. Most people with OCD also have significant generalized anxiety. The usual approach is to treat the OCD first, partly because it’s generally more disabling and partly because running both treatments simultaneously confuses everyone.
If the answer is OCD
The clinician you need is different. General anxiety training isn’t sufficient, and the screening question that matters is how they handle mental compulsions —the five questions are here.