Our growing mental health crisis is often presented as a recent problem. Too much social media. Too much exam pressure.

Casting blame on factors over which we have little control makes us all feel better. Blame Facebook. Blame the Department for Education. In other words blame anyone but us.

However it should be fairly self-evident that the main way we cope with life depends in large part on the security we get from what is going on at home.

Even here blame is deflected. The Early Intervention Foundation review for Department of Work and Pensions concluded that a high level of parental conflict is the main driver of family instability and teenage mental health problems.

Alas, this claim is easily disproved. No one doubts that it’s extremely unpleasant to be in a home where the parents fight. However it’s – thankfully – very much rarer than might be assumed. Just 2 per cent of parents quarrel regularly and are also unhappy in their relationship at any one time.

Last year, we published a study showing that 27 per cent of both boys and girls exhibit high or very high levels of mental health problems, whether these involve conduct, emotions, hyperactivity or peer relationships.

The biggest single factor was family breakdown.

This year we have looked in more detail at families who remain intact, using the same Millennium Cohort Study dataset of more than 10,000 mothers with 14-year-olds born in the year 2000 or 2001. We’ve also looked at the quality of the parents’ relationship, how happy the parents were in their relationship along the way, and whether they reported ever experiencing physical force – a broad measure ranging from pushing and shoving to hitting and kicking.

Our report can be viewed here, and was reported in the Mail and the Sun.

Let’s start with our findings on physical conflict. As with regular quarrelling, the use of physical force is mercifully rare. At any one stage, we found that a maximum of 4 per cent of mothers said they had ever experienced physical conflict and a further 4 per cent wouldn’t answer the question. So this is still a long way short of explaining how 27 per cent of boys and girls show high levels of problems. Quite clearly something else is going on.

That ‘something else’ falls into two main categories.

First, the relationship between parents matters. For boys, the single biggest factor above all others was whether their parents had been married from the start. That didn’t seem to matter for girls. What mattered for them was that their parents weren’t unhappy or in a low quality relationship or living with low income. In other words, so long as the situation at home was OK, girls were more likely to do OK.

Second, the relationship with the opposite-sex parent matters. On the face of it, having a close relationship with either parent seems to benefit teens equally. But when you throw all these other factors into the mix – parents’ marital status, happiness, relationship quality, use of physical force, education, ethnicity – it’s closeness to mum that matters specifically for boys and closeness to dad that matters specifically for girls.

What’s going on? Here’s what I think.

By age 14, teenage thoughts are beginning to drift towards their own romantic dream of reliable love and ‘happy ever after’, finding somebody somewhere who will share their life with them. What they see and experience in their home life will clearly influence how they imagine this dream might play itself out.

So if you get along with your opposite-sex parent, you are close to him or her and can chat about intimate personal stuff. That is bound to give you confidence that you are capable of having a close relationship with somebody of the opposite sex in the future.

But if you can’t get along, either because you’re not close to your opposite-sex parent or you have no contact at all, it’s going to cast doubt. Am I capable of fulfilling my dream? I don’t know. That leads to worry or misbehaviour. Girls tend to internalise more. Boys tend to misbehave more.

In addition, you’re looking for signs of commitment, reliability, trust. Research on adult commitment suggests that commitment for men tends to revolve around making decisions about the future whereas for women it’s more about attachment and bonding.

Maybe this is why sons notice whether their parents are married or not whereas daughters don’t, so long as the parents stay together. And so long as the parents aren’t doing too badly, daughters can maintain the hope that they can find reliable love.

It should be obvious that how your parents get on with each other and with you is so much more important than ‘social media’ or ‘exam pressure’. Teenagers who are confident in their home life are bound to handle modern-day pressures better. Those who struggle at home, or see their parents struggle, are going to find it harder.

So far as I know, this is the first study that attempts to link what teens experience from their parents with how they see their future relationship and how that affects their well-being.

What I am less clear about is what exactly it is about parents being married rather than unmarried that seems to affect boys particularly.

It could be that they are picking up on the symbols of being married – wedding rings, shared surnames, anniversaries. I think it more likely that married parents somehow reflect greater confidence in the way they relate because there is less ambiguity about the future compared with unmarried parents. This is definitely the case among new parents.

Either way, it’s really strong evidence that being married has a qualitatively different influence on teenage children, even compared with unmarried parents who stay together. And that is very much a choice over which we have responsibility.

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