Who hasn’t had a thought they can’t get out of their mind? Or had a random or inappropriate idea pop into their head? Or felt compelled to double-check and triple-check that the front door is locked? Such intrusive thoughts are normal. Typically they go away and we go about our lives.

But for some people, intrusive thoughts can become uncontrollable, persistent and invasive, and so they may try to alleviate them through compulsive rituals: repeatedly washing their hands, for instance, if they fear being contaminated from touching surfaces like doors and counter tops.

It’s at this point that we say the person has obsessive-compulsive disorder, or OCD.

But how exactly do the obsessive thoughts of people with OCD differ from the more garden-variety intrusive thoughts we all experience from time to time?

This is the question Jean-Sébastien Audet set out to answer in his Ph.D. under the supervision of Frederick Aardema, a professor in the Department of Psychiatry and Addiction at Université de Montréal.

Audet conducted a systematic review to determine what characteristics are specific to OCD compared to intrusive thoughts in the general population and in people suffering from anxiety and depression.

More frequent and long-lasting

Published in Clinical Psychology and Psychotherapy, Audet’s analysis showed that the intrusive thoughts of people with OCD are more frequent, last longer and create a need to act on the compulsion in order to neutralize their thoughts.

His findings underscore the significant distress caused by the intrusive thoughts associated with OCD.

“These thoughts provoke higher levels of guilt than in other anxiety-related disorders,” said Audet. “They are also experienced as more unpleasant, unacceptable and uncontrollable, and are associated with a higher degree of fear that the thought will become a reality.”

This distress is caused by the clash between the content of the intrusive thoughts and the person’s self-perception. The dissonance is particularly intense when the person has disturbing, forbidden thoughts such as “maybe I’m a pedophile” when in fact they have no such urges.

“People with OCD think their actions could put them in danger—for example, their carelessness could cause them to be robbed or get sick,” explained Audet. “By contrast, depressed people don’t believe they are a danger to themselves but are consumed by feelings of worthlessness, and people with anxiety perceive themselves as victims of external danger.”

Helping sufferers understand

Audet believes that delineating the characteristics unique to OCD can help sufferers and their loved ones understand the disorder and realize that the thoughts they have have no basis in reality. Determining those characteristics also facilitates early diagnosis and treatment.

In most cases, OCD responds well to medication and a type of therapy known as “exposure and response prevention.” This approach involves exposing people to situations that cause or trigger their obsessive thoughts and then helping them learn new ways of dealing with their anxiety instead of engaging in their usual rituals.

The research group headed by Aardema also recommends a type of therapy known as inference-based therapy.

“We think OCD is the result of a flawed narrative—a story that justifies the individual’s fears even though these fears have no basis in reality,” Audet explained. “Inference-based therapy helps the person see these false inferences and eventually stop their compulsive behavior because it no longer makes sense to them.”