PARIS: Watching a comedy film boosts the flow of blood to the heart, but watching a sad film makes the flow decline, according to a study published on Tuesday.

University of Maryland researchers got 20 young people to watch movie segments lasting between 15 and 30 minutes, taken from comedy films and serious films, with at least 48 hours between the two sessions.

With the help of ultrasound, the guinea pigs were measured for blood flow through the brachial artery, which runs between the shoulder to the elbow.

Blood flow was reduced in 14 of the 20 volunteers when they watched extracts such as the distressful opening scenes to “Saving Private Ryan”. But it rose in 19 out of 20 when they watched funny clips, such as scenes from “Something About Mary”.

The difference between the two flows was more than 50 per cent. Watching a sad movie has about the same effect on heart flow as doing mental arithmetic, it says. But watching a comedy is equivalent to a bout of aerobic exercise or starting a course of cholesterol-busting statin drugs.

Depression, anxiety, hostility and anger are already known to impair nitric oxide pathways that help blood vessels to dilate.

The authors tentatively suggest that a chuckle may stimulate selected hormones to have the opposite effect.

“Positive emotions such as mirthful laughter (may) have a (beneficial) effect on the endothelium,” the cells that line the walls of the blood circulation system, they speculate.—AFP