People who exercise regularly have a better chance of survival if they suffer a heart attack. However, a new study has found that those who exercise are also more likely to cope better mentally in the aftermath.

Norwegian researchers used data based on 120,000 people during three different time periods - 1984-86, 1995-97 and 2006-08. This allowed them to study how the health of a big group of people changed over time.

They then used a study sample of almost 200 people.

It is already known that depression is three times more common among people who have suffered a heart attack compared to people who have never suffered one. This study revealed that people who exercise regularly for a long time before a heart attack are significantly less likely to experience depression afterwards.

To be considered physically active for this study, a person had to exercise for a minimum of 150 minutes per week of moderate intensity or at least 75 minutes per week of high intensity.

The study found that among people who never exercised, 17% were depressed after a heart attack - this was found to be the most depressed group overall.

Among those who exercised during the first time period, 1984-86, but who had stopped exercising by the second time period, 1995-97, 12.5% were depressed after a heart attack.

Among those who did not exercise during the first time period, but who did train during the second period, 9% were found to be depressed after a heart attack.

However, among those who exercised regularly throughout the three time periods, just 7.5% suffered depression after a heart attack.

"Physical activity protects people from depression after a heart attack and it's never too late to start exercising," commented the study's lead author, Dr Linda Ernstsen, of the Norwegian University of Science and Technology.

Details of these findings are published in The American Journal of Medicine.