When you think about obsessive-compulsive disorder, or OCD, does being a “neat freak” or “germaphobe” come to mind?

In fact, OCD is not a personality quirk. It’s a distressing and disabling psychiatric condition that affects around one in 50 of us.

Read more: Obsessive compulsive disorder is more common than you think. But it can take 9 years for an OCD diagnosis

But up to half of those with OCD who receive the best psychological treatments don’t significantly benefit from them. This is likely because our understanding of OCD is incomplete.

It’s unclear what causes the disorder, and is likely a combination of genes, biology, and environment, including traumatic or stressful experiences.

In a recent study, we interviewed 16 adults with OCD. Our findings point to the role early experiences of rejection and trauma can play, for some people, in developing the disorder.

OCD is characterised by obsessions, compulsions, or both.

Obsessions are recurring, unwanted and intrusive thoughts, images or urges. They commonly centre on contamination, harm, symmetry, or repugnant themes such as unwanted sexual or violent thoughts.

Compulsions are repetitive behaviours (such as checking and re-checking the car is locked, or arranging objects so they’re “just right”) or mental acts (such as repeating certain numbers in your head). People perform these to directly address the feared consequences of the obsession and to ease distress.

For example, someone with OCD might believe someone they love will die or be injured if they don’t pray in a certain way or if they step on footpath cracks.

The disorder typically begins around age 20 and, without treatment, tends to be lifelong.

What’s behind intrusive........

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