The Simpsons is now in its 20th season. (Fox Broadcasting/Associated Press)

One of TV's most enduring cartoons, The Simpsons, may cause children to consider smoking because of its many scenes depicting the habit, according to a new study.

According to a study published in The Medical Journal of Australia, researchers say a lot of characters in the series smoke, which may influence children to consider taking up the habit.

Researchers Guy and Marielle Eslick viewed 400 episodes in the first 18 seasons of The Simpsons and documented 795 instances of smoking or references to smoking.

Guy Eslick — an epidemiologist at the Harvard School of Public Health — says most of the smoking instances involved male characters, but 20 per cent involved females, two per cent involved both sexes and 16 per cent involved non-gender characters, i.e. animals.

"Previous studies have highlighted the influence of on-screen use of tobacco by movie stars on adolescents, and the increased likelihood of these adolescents taking up smoking," the researchers wrote.

Even negative portrayals criticized

"Moreover, other research has found that very young children (aged 3-6 years) see, understand and remember cigarette advertising, and the use of cartoon characters like Joe Camel by RJR Nabisco has been reported to be more effective in marketing cigarettes to children than to adults."

The biggest culprits in the cartoon are Marge Simpson's chain-smoking sisters, Patty and Selma. The pair, who have raspy voices, have been smoking since they were teenagers.

In addition, Krusty the Clown and Bart Simpson's schoolteacher Mrs. Krabappel were also big offenders.

According to the study:

• Smoking was shown in a positive way in two per cent of the cases.
• In 35 per cent of the cases, smoking was depicted in a negative light.
• 63 per cent of smoking scenes were considered neutral.

The researchers noted that even "in instances of smoking being reflected in a negative way, particularly among younger characters, could have an impact on prompting children to smoke cigarettes."

The study concludes: "Viewing The Simpsons characters smoking may prompt children to consider smoking at an early age."

The Medical Journal of Australia is a peer-reviewed journal of the Australian Medical Association.