Married couples who manage to stay together for more than 20 years reported greater levels of happiness, new research has found.

These couples said that after two decades they felt happier and spent more time together doing shared activities.

The new research contrasts the existing belief that couples slide into a downward spiral after the initial honeymoon period of their relationship.

Paul Amato and Spencer James, the two men behind the study, told the Sunday Times that despite high divorce rates the outlook for marriages which last a lifetime remains positive.

Research shows that couples who are together longer than 20 years report high happiness levels

Levels of appreciation, closeness and contentment are also likely to increase after a significant amount of time together.

Harry Benson, research director at the Marriage Foundation, told the Sunday Times: 'In fiction, all of us have seen couples sitting in stony silence in restaurants, resigned to what looks like a dry and lifeless marriage.

'It's a depressing and misleading stereotype that sitcoms like to portray. And until now researchers have generally agreed that marriages start well but thereafter drift into terminal decline. Only it's a complete myth.'

However the researchers for this study realised that couples heading for divorce had been lumped together as had those with surviving marriages.

These couples said that after two decades they felt happier and spent more time together doing shared activities

But they failed to consider that their 'relationship trajectories' were completely different.

Similarly to the sitcom effect literature on marriage also tends to take the stance that happiness levels decline after years of marriage.

The researchers argued that an optimistic view of long-lasting marriages is not usually 'acknowledged or appreciated'.

Amato and James, from Pennsylvania State and Brigham Young Universities, looked at 20 years of data which observed 2,034 married people.

Some couple's graphs were pointing in a negative direction from the start if they were heading for divorce and showed signs of quarrels, hurt feelings, jealously and cheating

When the study, Changes in Spousal Relationships over the Marital Life Course, started a fifth had been married for less than five years, a fifth for more than 15 years and most from five to ten years.

Some couple's graphs were pointing in a negative direction from the start if they were heading for divorce and showed signs of quarrels, hurt feelings, jealously and cheating.

However those who were able to move past this stage developed a durability where they could move use their positive traits to settle arguments.

This pattern continued despite a couples level of schooling however divorce rates are lower for graduates.

The same can also be said for those in long-lasting second marriages with regards to levels of happiness.

It was discovered in the study that wives tend to report less marital happiness than men who appear to benefit from marriage more.

Sir Paul Coleridge, chairman of the Marriage Foundation, said that the findings reflected marriages well as the feelings about marriage are often reflected by stereotypes.

He added that research continually finds that people want a rewarding monogamous and lifelong marriage, which according to this research is a reality.