A University of Alberta study is helping crack the code to happiness by exploring the long reach of depression and anger over more than two decades.

The study, published recently in the Journal of Family Psychology, followed 341 people for 25 years, and found that negative emotions they may have suffered as young adults can have a lasting grip on their couple relationships, well into middle age.

The fact that depression and anger experienced during the teen years clung to people, even through major life events such as child-rearing, marriages and careers was surprising, said University of Alberta researcher Matthew Johnson.

"We assume or hope that high school experiences fade away and don't necessarily resonate 25 years later. The fact that symptoms of depression and expressions of anger can endure over many large events in life shows how important it is to deal with mental health early. Sometimes, problems don't just dissipate. How you grow and change over those early years becomes crucial to future happiness," said Johnson, an assistant professor of human ecology in the Faculty of Agricultural, Life and Environmental Sciences.

The research, drawn from a larger study begun in 1985, surveyed 178 women and 163 men through their transition to adulthood from age 18 to 25, again on their perceived stress levels at age 32, and on the quality of their intimate relationships at age 43, to find out whether anger or depression they may have felt as young adults was still affecting those bonds.

Findings point to the importance of recognizing that early mental health does influence couple relationships and that in turn, can have social costs later on, such as divorce and domestic violence.

As individuals, people can help themselves by "recognizing the fact that where they are in their couple relationship now is likely shaped by earlier chapters in their lives," Johnson added. "It's not only your partner's current behaviour or your current behaviour shaping your relationship, but the story you bring with you."