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The day after the general election Boris Johnson suggested that he wanted to cure the divisions caused by Britain's vote to leave the EU. Indeed, he urged "everyone to find closure and let the healing begin".

The use of the words "closure" and "healing" is significant.

In a poll last year, two thirds of people thought that Britain's exit from the EU was negatively affecting the nation's mental health.

If that's the case, then perhaps we should ask whether psychotherapy can tell us anything about why political events affect our emotions.

Or to put it another way: why is that we get so het up about political decisions when, by and large, they don't make much difference to our lives and, even if they did affect us, we can't do much about them?

This suggests that our emotions are caused by our thoughts. Dr David Burns, one of the founders of cognitive therapy, says: "Your moods are 100% caused by your thoughts.

"For example, when you're depressed you'll be telling yourself things like 'I'm no good. I'm a loser. Things will never change. I shouldn't have screwed up'.

"Or when you're angry with someone you're telling yourself, 'He's a jerk. He just cares about himself. He has no right to say that he shouldn't be that way'."

Media playback is unsupported on your device Media caption What makes you angry?

Distorted political thinking

These thoughts are often wrong according to Dr Burns.

"It's not only that your thoughts create all of your moods. But the thoughts that lead to depression and anxiety and anger are nearly always wrong thoughts. Depression and anxiety are the world's oldest cons."

Cognitive therapists call these incorrect thoughts cognitive distortions. There are many different types of distortions, and most are very recognisable. One of the most common is called "all or nothing thinking". This is where we look at things in black and white terms, rather than in shades of grey.

This distortion is particularly recognisable for anyone who studies politics and voters. We talk about our side as great, and the other side as hateful.

Rob Johns, professor of politics at the University of Essex, points out that this "tribal view where people tend to see everything on their side as brilliant, and everything on the other side as awful, was perfectly illustrated in the Brexit referendum".

Why do we get emotional about politics?

It's these kinds of thoughts that activate perceived threats to our side, which then make us angry, anxious or depressed about political events. And no-one is immune to this.

Matthew Parris, a columnist for the Times, former Conservative MP and ardent Remainer, says: "I think, I eat, I dream about Brexit. I get angry when I hear people espousing views that seem to me ridiculous; I shout at the radio."

He clearly recognises some of those cognitive distortions, such as all or nothing thinking, in himself.

"I see a ridiculous tendency to cast everything in terms of absolutely right or absolutely wrong, a disinclination to think that a middle position might be possible. I definitely see it not just in everyone else, but in myself too. The rage that a lot of us feel is out of all proportion."

Emotions affect what we do politically

These emotional reactions, such as Matthew Parris' anger, also affect our politics. In particular, these emotions have a big effect on whether we get involved.

While anger tends to make people participate more, it also has more negative effects. Lily Mason, a professor of government and politics at the University of Maryland, points out that angry people "don't really process information very analytically".

She says: "And so when they're angry, we have a very active electorate, but they are not really thinking very much about what they're doing."

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Anxious people are not much better. If I'm anxious, I'll try and find out more information, but anxiety will often prevent me taking it in. This means that anxious people aren't really better informed. And unlike anger, anxiety actually makes us less likely to get involved.

Emotions clearly shape our political behaviour, and not necessarily always in ways that we might want. After all, it's probably not great for democracy that angry people do the most, but know the least.

Are we an angrier nation?

Unfortunately, politics today seems angrier than ever. One possible reason for that is that we are more likely to interact with people who are similar to us.

That's partially about social media echo chambers, but it's also about our real lives. As Lily Mason argues in her book, Uncivil Agreement, people in the United States are now much less likely to meet those on the other side of the political divide and this has important consequences:

"When we don't have even acquaintances on the other side of the aisle, we don't think that they have the world's best interests at heart. We ascribe to them really, truly evil types of motivations."

The same could probably be said about politics over here.

Is there a solution? Would we perhaps all benefit from some therapy to address our distorted thinking about politics?

Maybe.

But people need to want to change and part of the problem is that it often feels good to embrace these distortions rather than reject them. Therapists often call this 'resistance'.

Feeling good to be angry

For example, Matthew Parris is happy to admit that his thinking is distorted and that it makes him over-emotional. But that doesn't mean that he necessarily wants to change.

"I can see that I'm going mad, and I'm damn well going to go mad," he says.

"There is a strange warped pleasure from it. I know that I have got it all out of proportion and I'm determined to keep it all out of proportion."

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Equally, it is also difficult to listen to the other side, as David Burns points out:

"Hatred is very rewarding to human beings. It feels good to fight and argue and you feel morally superior. You feel like I'm right and the other person's wrong. And to get close to the person you have to make a decision.

"Would I be willing to experience the death of my ego and my pride in order to get close to this person? And if you are, and many people aren't, then are you willing to examine your own role in the conflict rather than blaming the other person."

In the end, the cure for getting along with other people with different political opinions is often not about changing their minds. Rather, it is about changing ourselves.

The problem is that's probably the hardest change of all.

James Tilley is a Professor of Politics at the University of Oxford and a Fellow of Jesus College, Oxford. He presents Do Voters need Therapy? on BBC Radio 4 at 20:30 GMT on Monday 17 February.