Many of us have intrusive, unwanted thoughts sometimes, but we manage to brush them aside without them affecting our lives. But around three-quarters of a million people in the UK are thought to be living with severe, debilitating obsessive compulsive disorder - a mental health condition in which a person has obsessive thoughts and compulsive behaviours.
"My brain hung on to things - litter in the road, strangers sneezing too close on public transport," she says. "I'd close my eyes and see blackened tiles, seeping wounds and myself, jumping from a high bridge. And that was OCD. It's like the brain can't let anything go. It compulsively taunts itself with awful thoughts, and it becomes separate from me.
"It's a little like I'm searching for things which align perfectly with standards that I don't have," McQueen explains. "I stopped eating because I could never find the 'right' food. I didn't want to leave the house in case I saw something I didn't like to see, and those things ranged from anything from crying children to dirty light switches, being trapped unable to touch a door handle with a smudge on it and get my way back home."
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McQueen says she has become suicidal in the past and turned to alcohol. "I was hungry, thirsty but unable to sort out those things because the OCD told me that the food would turn to dirt in my mouth, that the water was rancid and that if I left my room to go to the bathroom, I would never be able to get back in again."
OCD also causes her to pick at her skin too. "I search for marks, spots, hairs, anything that I can remove, and cause a lot of damage to my skin," McQueen says, adding she is now on medication and having therapy.
What is OCD?
"OCD is often primarily concerned with experiencing anxious symptoms of heightened responsibility around the things that we care about," says Craig Shirley, a therapist and co-founder of the OCD Treatment Centre.
"This often leads the sufferer to become afraid of their thoughts, or environmental triggers that make them feel anxious. The person then performs behaviours known as rituals to control their anxious symptoms, which in turn only serves to give more meaning and importance to the thoughts," he adds.
"The person then gets more intrusive thoughts and increasingly feels the need to switch these feelings off more often, which eventually can become a debilitating cycle of thoughts, feelings and behaviours."
Unlike those who don’t suffer from OCD - who have meaningless thoughts they can ignore - someone with the condition will focus on the thought and begin to perform rituals to ensure the thought doesn’t come true, Shirley explains.
OCD goes far beyond the common perception of handwashing - and it can be extremely debilitating and disrupt all aspects of someone's life, from work to friendships and relationships. Simple tasks such as eating, cooking, washing or taking the rubbish out can become impossible.
"Another point worth noting is that often OCD can leave people feeling very depressed as well as having very low self-esteem, in which case these can also be factors for a person struggling to uphold a normal lifestyle," Shirley says.
Despite the severity of OCD, the term is commonly misused to describe people who like cleanliness or organisation - which diminishes the impact the condition can have on sufferers.
"One of the biggest misconceptions regarding OCD is that some people can be a 'little bit OCD'," Shirley says. Although we may occasionally have intrusive thoughts, have feelings of anxiety or be superstitious, it is not the same as having the condition.
Carrie Wheeler, 40, has OCD as well as other mental health conditions and multiple sclerosis. She says another misconception is that people with OCD are only obsessive regarding cleaning, but the condition can actually manifest in many different forms.
"I think the biggest misconception I know of is that all people with OCD are clean freaks. We do not all furiously clean our house or have an extreme fear of germs and wash our hands continuously," she says.
For Wheeler, OCD affects her home life and the way she eats, as her food must be prepared in a certain order. "If I lose something, I spend hours looking for it, staying awake until I find whatever it is - often keeping my husband awake while looking around in my bedroom for what it is," she says.
Whether someone develops OCD depends on a number of factors, including personality, genetics or life events. Although it is a chronic and debilitating condition, many people overcome OCD with treatment and support - or reduce the impact it has on their lives.
"There are many ways that a person can seek treatment for OCD," Shirley says. "The most common would be to visit your GP in order to explain your symptoms, before being referred to a specialist service such as a cognitive behavioural therapy (CBT) therapist."
With CBT, a person with OCD can learn to manage symptoms to regain an improved quality of life.
Shirley says CBT can be successful in the treatment of OCD, but other anxiety management tools can help alongside the therapy: "Often other principles, such as mindfulness and awareness of thoughts, education around the disorder and the brain’s role in the condition, as well as a very well-constructed relapse prevention programme for the person to follow once they finish therapy."
A therapy called exposure and response prevention can also be included as a part of CBT, which involves encouraging someone to face their fears and let obsessive thoughts occur without following them up with compulsions to 'fix' them.
Your GP or a specialist may recommend taking medication, but it depends on the individual. A type of antidepressant medication called selective serotonin reuptake inhibitors (SSRIs) can help alter the balance of chemicals in the brain. It can take weeks or months before you notice the effects of medication, which may also have side effects.
Seeking advice, information and support from organisations which specialise in OCD can help you understand more about the condition and how it can be treated, such as the charity OCD-UK. They can also help prevent isolation and offer a chance to socialise with others.
"It also helps tremendously to seek out a therapist who has had first-hand experience of the condition, as we find that many of our clients explain that this makes a big difference and helps them to feel understood whilst recovering from the condition."