Les had got it right about the in-laws

The first major academic study of mothers-in-law has come to the same conclusion as Les Dawson – they can affect the success of a marriage.

The first major academic study of mothers-in-law has come to the same conclusion as Les Dawson – they can affect the success of a marriage.

And the influence of in-laws goes on well beyond the early years of a marriage, according to behavioural scientists who carried out investigations in 450 extended families for the pioneering research.

From an analysis of the replies they received, the researchers say that the impact of uneasy relations with in-laws can damage marriages even after 20 years.

"We believe this is the first study to demonstrate that negative relations with in-laws may actually lead to a relative decline in marital status," says a report in the Journal of Marriage and Family.

For the research, the team quizzed each of the families for two hours about their lives and relationships with in-laws. Husbands in particular were asked how happy they were with their mothers-in-law, and how much tension and disagreement there were. They were also asked, "How often do you feel that your mother-in-law makes too many demands on you?"

The researchers, from Iowa State University, say that marriages where men didn't get on with their mothers-in-law were less likely to be successful.

"We have demonstrated that even after an average of two decades of marriage, unhappiness and conflict with in-laws still lead to decreasing perceptions of marital success. This is significant because it implies that the influence of in-laws continues far beyond the early years of marriage when couples are probably most vulnerable. Perhaps the vulnerability never ends."