When it comes to bullying, we often think of playground tactics such as pulling hair and stealing lunch money. But actually it can take many different forms and go on long after childhood.

That’s why this Anti-Bullying Week we’re also focusing on adult forms of bullying, whether that’s at work or in our personal relationships.

Enter: toxic friendships, a particularly insidious way people can be made to feel manipulated and worthless in adulthood.

Toxic friendships can be hard to spot due to closeness and duration of the relationship. A close friend you’ve had for years may seem like an unlikely perpetrator, but sometimes people are so close you can’t see their behaviour for what it is.

“It takes a fair bit of candid, quiet introspection to spot a toxic friendship,” explains Kate Leaver, journalist and author of The Friendship Cure (out 22 March 2018).

“Friends are meant to lift you up and make your life actively lighter – if they’re not doing that, or worse, actively making your life harder, than it’s time to consider getting out of the friendship.”

While all relationships are different, there may be some common behaviours and signs to look out for.

For Anjula Mutanda, a relationship psychologist and ambassador for Relate, a UK relationship charity, a key sign of a toxic friend is criticism: “They belittle your achievements – whether that’s a pay rise or a new boyfriend – and put you down. They won’t celebrate you, but pick holes and faults in your achievements.”

Kate adds: “It can be quite similar to the signs of a emotional abuse in a romantic relationship: the tendency to control and manipulate, the ferocious insistence on loyalty, the isolation from other friends and family members.”

Does this person put you down? Gossip about you behind your back? Share secrets you told them in confidence? This may sound like high-school behaviour but all have been associated with toxic behaviour.

It’s worth noting that there is no hard and fast rule on how these behaviours play out, everyone’s definition of a toxic friendship is going to be different.

Ultimately, the indicator of a toxic friendship is how that friend makes you feel and behave.

Anjula says: “If you notice you feel drained when with them or stressed or more self-critical, that tells you something in that relationship isn’t good for you. This relationships is costing more than rewarding.”

You may find your behaviour tends to alter around them, like you’re walking on eggshells to avoid conflict or criticism. Over time this can greatly impact your self-esteem and mental health.

I’d say toxic friendships can impact the victim by diminishing their self-esteem, making them feel threatened, unsafe or out of control, or habitually let down by the same person. It can have serious consequences for someone’s happiness and ability to socialize with other people.

Anjula questions whether a toxic friend was ever a friend in the first place: “I find the whole idea an oxymoron, I think it’s more like poisonous connections… This person is quite critical and judgemental, while calling you their friend. It’s confusing and feels like you’ve been slapped in the face.”

In an attempt to understand what might cause someone to treat a so-called friend in this way, know that it’s not you, it’s them.

Anjula is adamant about this. “It could be they feel jealous or inadequate. They may just like to dominate another person. If they stand back and look at themselves, they’re likely to be projecting their own disappointments onto others.”

If you recognise any of the above in a friendship you currently have, the advice is simply: face up to it. While might be painful, it’s worth it in the long run.

If in your heart of hearts, the friendship is worth saving, sit down with them and explain that you need things to change.

Otherwise, take the plunge and end the friendship.

Having a face-to-face meet-up to explain your position would be the best course of action, but if that isn’t possible send them a text message or an email.

Kate says you may even want to consider ghosting them (as a last result, of course): “If that person either won’t listen or will create more drama with any sort of confrontation, it can be effective to freeze someone out and withdraw contact.”

Nowadays friendships exist online as well as IRL, so simply avoiding the former friend at social events may not get them out of your life completely.

“On social media there is no harm in unfriending and unfollowing someone,” Anjula explains. “It acts as a good signal that you are stepping out of the arena.”

Once the deed is done, you need to refocus on looking after number one. Spend time with positive people who build you up and doing things you enjoy.

Breaking up with a friend and suddenly having them out of your life can feel like a regular romantic break-up or like a death. Do not underestimate this, take time for yourself to grieve.

Kate says: “I think we seriously underestimate the damage a toxic friend can do – we still dismiss friendship as being less important than romantic love and so we don’t invest as much time processing what sort of friendship damages us.”