When we talk about obsession, we rarely see it with all its nuances.

The term usually conjures up one-dimensional images of someone frantically scrubbing something clean or a fixation on one thing (from a Mac lipstick to an Instagram influencer), but it’s something that possesses multiple strands.

And with new four-part psychological thriller Cheat airing on ITV this week, where obsession between a professor and a student has devastating consequences, it got us thinking.

We asked psychotherapeutic counsellor Chanelle Sowden about the different forms of obsession and how they manifest themselves…

People with particularly tidy homes are prone to laughing off their orderliness with phrases like, ‘I’m a bit OCD’, but an obsession with avoiding dirt is a very real and very serious condition.

“This is the need for things to be perfect, correct, even, exact, symmetrical, equal, or for everything to be remembered,” says Sowden.

“Often when things feel chaotic in our heads, it can help to have order and control in our environment. After a while, we can wire ourselves to feel some level of relief when things are in control around us.

“This behaviour can lead to an emphasis on neatness, needing to be 100% correct, overthinking and control over our belongings – either keeping them to a minimum, or hoarding so nothing gets forgotten.

“The relief and safety gained by getting or keeping something perfect can create enormous pressure and requires us to take extreme action.”

While wanting to spend a lot of time with someone you’re involved with or interested in is nothing to trigger alarm bells, as we see in ITV’s Cheat, this can evolve into something more dangerous.

“Infatuation or obsessing about another person, romantic or not, is common,” says Sowden.

“It can play out in relatively harmless ways, such as celebrities we idolise, secret work crushes, or identifying with a certain author or even a stranger. It can also play a big part in the early stages of ‘falling in love’. 

“Obsessions can vary in intensity, though. When our relationship with another person goes beyond the point of what is healthy and good for our mental health, there can be signals. 

“Our thoughts or emotions may feel overwhelming, uncontrollable or all-consuming. They may also become unpleasant or unwelcome. 

“Extreme obsessions can trigger sabotaging behaviour, delusion or risky urges.”

Few of us would welcome the idea of falling ill or living in filth, but for others this can become all-consuming.

“Contamination obsession is a fear of germs, disease, dirt, ingesting something unwanted or coming into contact with household cleaners or other chemicals,” says Sowden.

“The behaviours this obsession causes include excessive washing, cleaning and hypervigilance around consuming foods prepared by someone else. 

“This can lead to avoiding certain social situations such as restaurants, eating at other people’s houses, swimming pools or avoiding contact with other people or animals.”

Most of us have moments of guilt and worry about how our actions could influence other people. But one strand of obsession can take this to frightening levels.

“A deep fear of blame or being responsible for something ‘bad’ happening, such as ruining something or hurting themselves or someone else, is often at the root of this,” explains Sowden.

“This fear can lead to excessive checking of locks, gas hobs, hair straighteners, candles, health checks, pregnancy or repeatedly needing reassurance from others. 

“Although worrying about these things is common and understandable, it can lead to disruptions in everyday life, such as avoidance or limiting behaviours with regards to relationships, our job, our commute or having potentially harmful items around us such as knives.”

For some, obsession means distressing and repetitive thoughts that enter their head without invitation.

“Intrusive thoughts are involuntary and often revolve around being out of control in some way,” Sowden reveals.

“They may include magical thinking that doesn’t make logical sense. 

“We all have involuntary intrusive thoughts – some can be positive, which we might call ‘daydreams’.

However, if they become negative, repetitive and centre around relationships, violence or sexual thoughts, it can feel overwhelming and distressing, and lead to harmful behaviours.”

Delve into a world filled with obsession and the consequences of it with Cheat, which continues tonight at 9pm. Catch up on the series so far on the ITV hub.

If you feel you’re struggling with addictive, obsessional or compulsive thoughts or behaviours, speak to your GP or consult a mental health professional for advice and support.