What is 'Pure O', the form of obsessive compulsive disorder at the centre of Channel 4’s Pure?

Marnie is suffering from 'Pure O', a form of obsessive compulsive disorder.

• Everything you need to know about Pure on Channel 4
• 23 TV shows written by women to look forward to
• Stay up to date with the RadioTimes.com newsletter

Channel 4’s strikingly bold new series is a fictionalised adaptation of Rose Cartwright’s memoirs about her experience of a very real, but little-known, condition.

Find out more about the illness below – and discover why Cartwright described the adaptation of her book as the “best therapy” she’s ever had.

What is Pure O?

Pure obsessional OCD, nicknamed Pure O, is a form of obsessive-compulsive disorder in which people experience obsessions without necessarily having external compulsions.

The condition manifests itself in distressing, intrusive thoughts or mental images, which tend to revolve around themes including: harm to self and others; worries about sexual orientation and relationship decisions; fear of doing something illegal; paedophilia; and over-concern for honesty or religious purity.

Although most people experience fleeting unwanted thoughts from time to time, they are able to dismiss them as uncomfortable and move on. Sufferers of Pure O, on the other hand, become anxious about these thoughts and can begin to obsess over them, unable to get them out of their head.

Pure O, therefore, is not the experience of having intrusive thoughts – but the reaction to them and the inability to make them go away.

Rose Cartwright’s website, Intrusive Thoughts, further explains that many Pure O sufferers are perfectionists and have a high standard “for what their brain ‘should’ be thinking”.

Pure O sufferers “spend time analysing why they are having these thoughts and what the thoughts say about them as a person… failing to meet this standard of control over their own brain will lead them to conclude that they are a bad person or a monster”.

The writer of Channel 4’s Pure, Kirstie Swain, also refers to the anxiety that intrusive thoughts can create which leads sufferers to question who they really are and what their desires are. “Sometimes you don't know where a mental disorder ends and you begin,” she says.

According to the mental health charity Mind, people with Pure O show "no external signs of compulsions" such as checking and washing, but they still experience mental compulsions: for example checking their emotions or checking whether they are aroused by a particular intrusive thought.

Is Pure O easily diagnosed?

“This is something that people live with in secret, that they're deeply ashamed of, that they feel they can't talk about,” says Rose Cartwright. “When I was 15 and I first started experiencing this, this definition didn't exist in the public eye.”

Because of the shame attached to intrusive thoughts and common misconceptions about OCD, many sufferers go years without seeking help, therefore not being diagnosed.

In the Channel 4 show, Marnie mistakenly presumes she must be a sex addict, even though the thoughts she is having are distressing as opposed to arousing.

She then discovers she has OCD, but the show’s writer Kirstie Swain says that “even if you get the label you're looking for, that doesn't solve your problem”.

“You still have to deal with the fact you have this mental illness,” she explains. “Marnie's so sure that finding a label for herself is going to solve the problem but actually for a while it makes things worse….

“OCD is so repetitive: it doesn't have a beginning, middle and end. It has a beginning and a middle and a middle and a middle and it goes on without an end in sight.”

Is Pure O treatable?

Exposure therapy is “remarkably effective” in treating OCD, according to the Intrusive Thoughts site. This treatment involves purposefully provoking unwanted, distressing thoughts and images while simultaneously resisting the urge to seek relief.

Cartwright’s website also recommends medications such as selective serotonin uptake inhibitors (SSRIs).

What was it like for Rose Cartwright to have her memoirs adapted?

Cartwright, who still has OCD but has been through effective therapy so that she can “catch myself when I'm going down those compulsive spirals”, speaks abut the catharsis of making Pure.

She says: “Just being involved in a project like this has become part of my healing process. I've had a lot of therapy and this is definitely the best therapy I've had.”

Cartwright describes the experience of visiting the set of Pure while an intrusive thought sequence was being filmed with naked extras.

“It was the 'Beast from the East' so it was snowing, which is terrible for naked extras. And I was like, 'What have I done?' and I turned the corner in Shoreditch and I looked down the street and it was just floodlights, and 60 guys in high vis jackets. I was like, 'Wow, this is incredible.'

“Then I got closer and they were actually shooting an intrusive thought, down the alley way, and I heard someone shout, 'OK, we're going to do the intrusive thought now.' And they pulled up these big privacy screens and the guys in the salon down the alley had to be briefed that there might be some nudity happening outside just in case their clients got offended. It was like, 'What is my life?'

“It was such a privilege, because people pay hundreds of pounds for that kind of exposure therapy and here I am, I had this thing I'd kept secret and was so ashamed of. But going down to set and just seeing it discussed so openly and for storytelling to be such a healing tool, I was just like, 'This is alright, I don't regret this.'"

Pure begins at 10pm on Wednesday 30th January on Channel 4