Relationships are complex things, and what might work for one couple (an open relationship, for example) might not work for another.

That's all well and good as long as both (or all) people are on the same page and are treating each other with respect.

A toxic relationship, however, by its very nature serves nobody. Defined by Psychology Today as "any relationship that is unfavorable to you or others", the repercussions of remaining in a toxic relationship can be serious, particularly when it comes to mental health.

What constitutes a toxic relationship?

"Relationships are all about change; accepting each other's differences and adapting to the changing needs of each other, the relationship and the environment. Good relationships are agile, dynamic and flexible," psychologist and relationship expert Melanie Schilling told HuffPost Australia.

"Toxic relationships tend to be rigid and inflexible. One or both partners are intolerant of the other's differences and there is a lack of respect in communication. Often, partners communicate through fear or threats and negative consequences are inevitable."

5 signs you're in a toxic relationship

One or both of you are unwilling to accept the others' differences.

Only one of you (or neither of you) has the opportunity to express your needs.

You communicate with blame, contempt and/or resentment and neither partner takes responsibility for issues.

Manipulation and/or coercion are used as tools and point scoring becomes a sport.

One or possibly both of you experience intense feelings of inadequacy and low self worth.

What should you do if you're in a toxic relationship?

According to Schilling, there are key things to do if you suspect you might be in an unhealthy partnership.

"The first is to set and maintain healthy boundaries," Schilling said. "Take care of yourself first and be clear about what you are comfortable and uncomfortable with.

"Examine your role. Think about how you might be contributing to the toxic dynamic, for example, making excuses for them or trying to fix them.

"Lastly, if you're overwhelmed or unsure how to take the next step, seek professional help from a psychologist."

Is it ever okay to stay in a toxic relationship?

"Not if you value your own mental health, or that of your partner," Schilling said.

And while it may seem like no one in their right mind would want to stay in a partnership of this kind, Schilling points out it's often not as simplistic as it may seem.

"Toxic relationships can become strangely comfortable," she said.

"As humans, we are creatures of habit and sometimes we subscribe to 'better the devil you know'. The key is to recognise when you are in an unhealthy relationship and take action to change it."

What are some signs your partner is emotionally manipulative?

According to Schilling, the key here is to pay attention to how YOU feel and look for these signs:

You are emotionally caught up in their drama

You dread or even fear being around your partner

You feel exhausted and drained by them

You feel embarrassed or ashamed of yourself for being in the relationship

You notice yourself constantly trying to fix your partner.

How should you go about exiting a toxic relationship?

"If you've tried talking to your partner, setting new boundaries and have attempted to find common rules for engagement, but things are still toxic -– get out," Schilling advised.

"Surround yourself with a support team of your best cheerleaders (and a psychologist if required) and take steps to remove yourself."