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It is normal for parents to argue, but the way these disagreements affect children varies greatly. What can parents and carers do to limit the harm caused by their rows?

What happens at home really does affect children's long-term mental health and development.

But it is not only the relationship between the parent and child that is important.

How parents get on with each other also plays a big role in a child's wellbeing, with the potential to affect everything from mental health to academic success and future relationships.

But there is the chance for some good to come out of a "positive" row.

In most cases, arguments will have little or no negative effects for children.

But when parents shout and are angry with each other, when they consistently withdraw or give each other the "silent treatment", problems can sometimes arise.

UK and international research conducted over several decades through observations in the home, long-term follow up work and experimental studies, suggests that from as young as six months, children exposed to conflict may have increased heart rates and stress hormone responses.

Infants, children and adolescents can show signs of disrupted early brain development, sleep disturbance, anxiety, depression, conduct disorder and other serious problems as a result of living with severe or chronic inter-parental conflict.

Image copyright PA Image caption Children's academic performance can be affected by exposure to ongoing conflict

Similar effects are also seen in children who are exposed to ongoing but less intense conflict, compared with children whose parents constructively negotiate or resolve conflicts.

Nature or nurture?

The impact on children is not always as might be expected.

For example, divorce - and parents deciding to live apart - has often been seen as having a particularly damaging and lasting effect on many children.

But in some cases, it is now thought that it could be the arguments that take place between parents before, during and after a separation that do the damage, rather than the break-up itself.

Similarly, it has often been assumed that genetics play a defining role in how children respond to conflict.

And it is true that "nature" is central to a child's mental health - playing a part in problems from anxiety, to depression and psychosis.

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But the home environment and the "nurture" they receive there can also be very significant.

Increasingly, it is thought that underlying genetic risks for poor mental health can be made worse - or better - by family life.

The quality of the relationship between parents appears to be central, whether or not they are living together, or if the children are genetically related to the parents or not - for example, if they were conceived using donor eggs or sperm, or adopted.

Rows about children

What does all of this mean for parents?

First, it is important to recognise that it is perfectly normal for parents and carers to argue or disagree with each other.

However, when parents engage in conflicts with each other that are frequent, intense and not resolved, children do less well.

Even more so if the row is about children, for example where children blame themselves or feel at fault for the arguments.

These negative effects can include sleep disturbance and disrupted early brain development for infants, anxiety and conduct problems for primary school children, and depression and academic problems and other serious issues, such as self-harm, for older children and adolescents.

Image copyright Getty Images Image caption Children who feel isolated because of parental conflict can struggle to form relationships

For decades, we have known that domestic abuse and violence can be particularly damaging for the children involved.

But parents don't even need to display volatile or aggressive behaviour towards one another for damage to be done.

Where they become withdrawn, or express low levels of warmth for each other, children's emotional, behavioural and social development is also put at risk.

The problems don't end there.

Not only are children affected in their own lives, but research shows that bad relationships can pass from one generation to the next.

It is a cycle that needs to be broken if we want positive and happy lives for today's generation of children, and the next generation of parents and families.

Arguing in 'private'

But there are factors which can reduce the harm caused.

From the age of about two - and possibly from an even younger age - research tells us that children are astute observers of their parents' behaviour.

They often notice arguments - even when parents think their children don't, or believe they have protected them by arguing in "private".

What matters is how children interpret and understand the causes and potential consequences of conflicts.

Based on their past experience, children decide whether they think conflicts are likely to escalate, potentially involve them, or could even pose a risk to family stability - a particular concern for some young children.

Image copyright Getty Images Image caption Boys and girls may react differently to their parents' arguments

They may also worry about the possibility of their relationship with their parents worsening as a result.

Research suggests that boys and girls may also respond differently, with girls at greater risk of emotional problems, and boys at greater risk of behavioural problems.

Often, policies aimed at improving mental health among the young have focussed on supporting the children themselves, or in directly supporting parenting.

But it could be that supporting the relationship between parents could also make a big difference to children in the short term, as well as better equipping them to form their own healthy relationships with others in the future.

Where children have supportive relationships with relatives, siblings, other adults (eg teachers) and friends, these are important for children's long-term healthy development. What happens at home can significantly influence these relationships, for good or ill.

It is natural for parents to feel concerned about the impact their arguments may have on their children.

But it is normal to argue or disagree sometimes, and in fact children respond well when parents explain or resolve - in an appropriate way - what an argument was about.

Indeed, where parents successfully resolve arguments, children can learn important positive lessons which can help them navigate their own emotions and relationships beyond the family circle.

Helping parents understand how their relationships affect children's development sets the stage for healthy children today - and healthy families in the future.

About this piece

This analysis piece was commissioned by the BBC from an expert working for an outside organisation.

Prof Gordon Harold is the Andrew and Virginia Rudd professor of psychology and director, Rudd Centre for Adoption Research and Practice at the University of Sussex.

He recently published a comprehensive review of research in this field in the The Journal of Child Psychology and Psychiatry, which you can read online along with a detailed bibliography.

Edited by Jennifer Clarke and Duncan Walker.