Obsessive-compulsive disorder
A disorder of a hyperactive cortico-striato-thalamo-cortical 'error-detection' loop that generates intrusive doubt the mind cannot dismiss, and compulsions that relieve anxiety just enough to entrench the loop further.
First principles
OCD is a fault in the brain's error-detection and doubt-resolution circuit
A cortico-striato-thalamo-cortical loop (linking orbitofrontal cortex, striatum and thalamus) normally checks whether an action or thought is 'complete' or 'safe' and then switches off, allowing attention to move on. In OCD this loop is hyperactive and fails to switch off, so the brain persistently signals that something is wrong, unfinished or dangerous even when it is not. The conscious experience of this miscalibrated signal is the obsession: an intrusive, unwanted thought, image or urge that recurs despite the person recognising it as excessive or irrational.
Educational content pending clinical review. Not medical advice.