A new Dutch and Canadian study of young men's drinking behaviour while watching an hour of TV (a movie clip with advert breaks) found that, compared to those who did not see much alcohol portrayed on screen, those who saw alcohol portrayed frequently, on average consumed 1.5 more 200 ml bottles of alcoholic beverage.

The study was the work of scientists from the Behavioural Science Institute at Radboud University Nijmegen and the Research Centre for Adolescent Development in Utrecht University, both in The Netherlands, and colleagues from the Department of Psychology at Queen's University in Kingston, Ontario. It was published for online access on 4 March in the Oxford University Press journal Alcohol and Alcoholism.

First author Rutger Engels, professor in developmental psychopathology at the Behavioural Science Institute, Radboud University Nijmegen said that:

"This is the first experimental study to show a direct effect of exposure to alcohol portrayals on TV on viewers' immediate drinking behaviour."

In their background information the researchers described how movies and adverts generally put alcohol in a positive light and the assumption is that this encourages young people to drink it. So they decided to set up an experiment to test it.

They designed a naturalistic setting (which they described as a "bar lab") where friendship pairs of young men could watch a movie "home cinema" style for 1 hour, including 2 commerical breaks. While they did this they had access to a fridge filled with alcoholic and soft drinks. The idea was to replicate an observable version home-based TV viewing.

The researchers recruited 80 male university students aged from 18 to 29 and randomly assigned them to one of four groups (20 in each group), characterized by the frequency with which alcohol was portrayed in the movie and the commercial breaks:

1. Movie and adverts with many positive portrayals of alcohol. The film was American Pie, and the participants saw 18 instances of characters drinking alcohol and 23 other instances where alcoholic drinks were shown. The commercial break also included adverts for alcoholic drinks.

2. Movie with many and adverts with no positive portrayals of alcohol. The film for this group was also American Pie with the same exposure as in group 1, but the commercial breaks showed no adverts for alcohol.

3. Movie with few and adverts with many positive portrayals of alcohol. The film was 40 Days and 40 Nights during which the participants only saw characters consume alcohol in 3 instances and there were 15 other instances when alcoholic drinks were shown. The commercial break also included adverts for alcohol.

4. Movie with few and adverts with no positive portrayals of alcohol. The film for this group was also 40 Days and 40 Nights and the commercial break had no adverts for alcohol.

The results showed that:

* Over the period of an hour, the young men in group 1, who watched the film with many positive portrayals of alcohol, together with commerical breaks containing adverts for alcohol, consumed an average of nearly three 200 ml bottles of alcoholic beverage.

* The young men in group 4, who watched a film with few positive portrayals of alcohol and saw no adverts for alcohol only drank an average of 1.5 bottles of alcoholic beverages in an hour.

* The most alcohol anyone consumed was 4 bottles and the least was none.

The researchers concluded that this study is the first to show that there is a "causal link between exposure to drinking models and alcohol commercials on acute alcohol consumption".

Engels said the study clearly showed that portraying alcohol in films and adverts not only influenced people's attitudes about drinking within a culture or society, but might also have a direct effect on behaviour, such as triggering a craving in people who already consume alcohol.

"While watching an ad for a particular brand of beer, you are not only more prone to buy that brand next time you are in the supermarket, but also that you might go immediately to the fridge to take a beer," Engels suggested.

The researchers said if their findings are replicated in other studies this should be a wake up call for policymakers, inasmuch as:

"If moderation of alcohol consumption in certain groups is strived for, it may be sensible to cut down on the portrayal of alcohol in programmes aimed at these groups and the commercials shown in between."

Another implication, they wrote, may be that:

"In situations in which this is possible (eg cinemas), availability of alcohol should be reduced when movies and commercials contain alcohol portrayal and individuals in a group at risk for problematic drinking are present."