Have you ever left your house in the morning and convinced yourself that you left the iron on or the front door open? You’re not alone. A recent study involving 13 countries around the globe has found that 94 per cent of us have experienced this type of unwanted thought.

These intrusive thoughts (“did I leave the iron on?”), images (picturing your house on fire) and impulses (the urge to shout loudly in a library) are actually symptomatic of obsessive-compulsive disorder (OCD).

The study, which was conducted by researchers from Concordia University in Montreal, assessed 777 university students across six continents. Participants were questioned about the occurrence of unwanted thoughts such as “did I lock the front door?”

Researchers found that these thoughts, images and impulses are “widespread”, a conclusion that will assist in the treatment of those affected by the more complex Obsessive-Compulsive Disorder.

“This study shows that it’s not the unwanted, intrusive thoughts that are the problem – it’s what you make of those thoughts,” explains Professor Adam Radomsky, in the Journal of Obsessive-Compulsive and Related Disorders.

For example, Professor Radomsky says that most people who experience an intrusive thought about jumping off a balcony would just tell themselves that it is a strange or silly thing to think. But a person with OCD would worry about the thought and what it could mean.

“People suffering from OCD experience intrusive thoughts more often and are more upset by them, but the thoughts themselves are actually really common,” said professor Radomsky.

Professor Radomsky believes that this news will be reassuring to patients with OCD. “People with OCD and related problems are very much like everyone else,” he explains.

“And that’s at the heart of our cognitive and behavioural interventions for helping people overcome OCD.”

So what is the difference between those experiencing “unwanted intrusive thoughts” and those experiencing full-blown OCD?

“We only define these obsessions and compulsions as a disorder when they cause the person significant distress and start to interfere with their ability to go about their daily activities,” says Dr Rebecca Anderson, psychology lecturer at Curtin University.

Those who experience severe OCD can find it difficult to maintain their work, family and social commitments. Some sufferers believe that if they don’t perform a compulsion a certain number of times then “something bad” will happen to them or to a loved one.

“For one client, this meant getting out of bed three times, brushing their teeth three times, putting every item of clothing on three times, locking the house three times and so on,” Dr Anderson explains.

“You can imagine how long it would take to just get out the door each morning. The extent of the rituals had meant they were at risk of losing their job due to being late every day.”

It is estimated that as many as 500,000 Australians are affected by OCD. There are several well-documented types of OCD. Obsessions include a fear of contamination, concerns that a loved one will come to harm, a need for symmetry or preciseness. Common compulsions include excessive hand-washing, repeating everyday tasks or bodily motions and arranging items in a particular way.

Dr Anderson notes that to a certain extent it is normal to like having things a certain way. However, she also says that: “if having to have things a particular way is impacting on your everyday life, work and relationships it might be something you need to work on.”

We probably all know someone who is a compulsive tidier or obsessive about things being in their place. But 28-year-old administrator, Megan Baker* has been known to take her organising preferences further than most.

Baker, who has been diagnosed with “obsessive-compulsive tendencies,” likes things to be properly organised, which includes alphabetising books and DVDs. But during an episode she sometimes found herself reorganising the “big messy pile” of DVD’s in the JB Hi-Fi bargain bin.

“I did it in a few different stores, over about a year,” says Baker. “It made me feel in control.”

Baker says that since being treated for depression her obsessive-compulsive tendencies have been occurring much less frequently. But she still likes her own DVD collection to be meticulously alphabetised.

* Name has been changed

This article first appeared on ‘The Sydney Morning Herald’ on 28 April 2014.