What the longest study on happiness tells us

For 75 years the Harvard Study of Adult Development tracked the lives of 724 men. Women were only added in the second generation of the study.

Each year they were asked about their work, their home lives and their health, in an attempt to crack the code of a good life.

Good relationships, with family, friends, colleagues and community, keep us happier and healthier.

So which one of your resolutions this year is about building better relationships?