If you think stress is affecting your health, it probably is. That's the conclusion of an long-term study that found that people who thought stress was affecting their health a lot had a much higher risk of suffering a heart attack.

The study looked at over 7,000 London-based civil servants, aged 35-55 over 18 years. From 1991 to 1993, participants were asked how much stress or pressure has/had affected their health: not at all, slightly or moderately (the low group), or a lot or extremely (the high group).

People who think stress has a big effect on their health have a much higher risk of suffering a heart attack.

Study subjects were then followed for 18 years and the number of heart attacks they suffered was recorded. Depending on exactly how the researchers analyzed the data, the increase in the risk of heart attack among people who thought stress had a major effect on their health (who believed, for example, that it kept them up at night or contributed to digestive problems) ranged from 50% to more than double the risk.

The raw, unadjusted percentages of heart attacks that occurred over the 18 years were: 4.5% in people who claimed no health effect from stress, 4.6% in people who claimed a slight or moderate effect, and 8.2% in people who claimed stress had affected their health a lot or extremely. This is an 82% increase in heart attack risk in the group claiming stress had a strong effect compared to the "no health effect" group.

The researchers knew that other factors could easily play a role in these results. For example, 55-year-olds have a greater risk of heart attack than 35-year-olds and smokers have a greater risk of heart attack than non-smokers. So they "adjusted" their raw data to accommodate these and other differences.

When the heart attack risk was adjusted for factors like sex, age, ethnicity, marital status and employment grade, people who said their health was affected a lot or extremely by stress had 2.12 times the risk of suffering a heart attack over the 18 years than people who said stress had no effect on their health did.

When they looked at behavioral factors such as smoking and alcohol consumption, biological risk factors such as diabetes, psychological factors such as social support, there was a 49% increased risk among those who thought stress was bad for them.

Whichever of the three methods of analyzing the data is actually the most meaningful, they all provide evidence for the fact that that people who think stress has a big effect on their health have a much higher risk of suffering a heart attack.

The study authors see this finding as a wake-up call for doctors to take their patients' complaints of stress and stress-related health problems more seriously, suggesting ways to reduce stress.

And for people who are stressed, it's one more reason to de-stress. It's true that lowering stress brought on by a loved one or boss is sometimes easier said than done. But it's equally true that most people can lower the amount of stress in their life. Getting enough sleep and eating a better diet are two of the simplest ways to do so.

The study is published online by European Heart Journal and will also appear in a future print edition. The article is freely available.