“Obsessions are intrusive and unwanted thoughts, feelings and sensations while compulsions are repeated, ritualised acts that are done to neutralise or alleviate the anxiety caused by the obsessions,” Nina tells the BBC’s Complex podcast.
Around 1- 4% of the population is thought to live with OCD but the number of 16-24 year olds in England reporting symptoms of it has more than tripled in a decade.
The condition is now the second-most widespread mental health disorder for young adults, a major NHS England survey suggests.
Intrusive thoughts can be extremely distressing and often focus on topics that feel completely at odds with a person’s values or identity.
“You might have thoughts about harm coming to loved ones,” says Nina.
“It could be questioning one’s sexual attraction, thinking are you homosexual? Are you heterosexual? It can even be as extreme as worrying are you a paedophile?
“A really common one is intrusive thoughts about contamination and worries about getting ill or spreading sickness,” she says.
OCD most commonly begins in puberty or early adolescence, but some people are diagnosed later in life as they can “go years masking or covering up the distress,” she says.
Research suggests there may be a genetic component to developing OCD as well as links to early life stress such as bullying, bereavement or family breakdown, she says.