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Evidence-Based Prevention

The idea that prevention is better than a cure is commonly held by the public and by health care professionals. It makes sense, it seems to be a good thing, and why aren't "they" spending more on prevention?

There are some outstanding examples of prevention. Smallpox eradication must be the public health triumph of the century, though the apparent success of many vaccination programmes was achieved on the back of incidence rates that had been falling steadily and substantially for decades.

What about telling people not to do things. Does that work, and is there any evidence that it does? A study from the USA [1] indicates that drug prevention programmes targeted towards teenagers can produce meaningful and durable reductions in tobacco, alcohol and marijuana use.


In the Spring of 1985 56 junior high schools in three areas of New York State were assessed to determine existing cigarette smoking levels. From within groups of schools with similar levels of cigarette smoking, schools were randomly assigned to one of three interventions:-
  1. Prevention programme with a formal 1-day training workshop and implementation feedback.
  2. Prevention programme using videos and no implementation feedback.
  3. No special intervention.
The prevention programme consisted of 15 periods taught in the 7th grade (12 year olds). The intervention was designed to teach students cognitive behavioural skills for building self-esteem, resisting advertising pressure, managing anxiety, communicating effectively, developing personal relationships, and asserting rights. It was also designed specifically to teach skills and knowledge related to resisting social influences relating to tobacco, alcohol or other drugs.

This programme was followed up in each of two subsequent years (8th and 9th grades) with additional intervention sessions, but not later.


The original sample was just under 6,000 students who entered the study in 1985. Of these, follow-up information could be obtained on just under 3,600 six years later in 1991. The follow-up sample was 90% white and had a mean age of 18 years in 1991.

A subgroup analysis was also carried out on those students who were judged to have received at least 60% of the intervention programme (high-fidelity sub-group). This comprised 2752 students.


Using data on the whole sample of 3597 students, the effects of both intervention programmes was to reduce cigarette consumption significantly - a reduction of 6% from 33% to 27% using cigarettes in any month. The proportion smoking 20 cigarettes a day was reduced by more than 20%. There was no difference in alcohol use, though problem drinking was reduced significantly by 6%. There were only slight differences in marijuana consumption.
For the high fidelity subgroup, there were significant reductions of 10% in cigarette smoking and 4% reductions in both alcohol and marijuana consumption. Problem drinking and heavy cigarette use in this group were reduced by a third and frequent marijuana use by almost half. The combined use of tobacco, alcohol and marijuana was reduced by 66% in this group.


Viewed by the crude results alone, the gains of prevention interventions may seem modest. However, these results were obtained six years after the intervention,. and indicate a powerful and long-lasting effect of an intensive and thorough prevention programme incorporating social skills training. Even modest gains spread over a large population can have immense health gains for society and individuals.

It was notable that in the sub-group which attended more than 60% of the classes the programmes had a much greater impact. Heavy smoking, heavy drinking and polydrug use were reduced by very large amounts - 25% to 66%. These are large gains.

This important study was randomised, was intensive, and had a long period of follow up. It is worth reading by all those involved in the design and implementation of health prevention programmes.

Social marketing makes a difference

Bandolier has also received a copy of a fascinating report on the usefulness of social marketing on tobacco, alcohol and marijuana use in Canada [2].

The Canadian Department of Health employed several health promotion social marketing campaigns on drugs and tobacco. The campaigns are based on social marketing principles and strategies, which recognise that informing the public about a particular issue will not, by itself, lead to changes in attitude or behaviour. Changing behaviour sometimes requires specific kinds of marketing - social marketing - which attempt to change perceptions, attitudes, opinions and behaviours that underlie an individual's health or lifestyle habits.

Social marketing employs a mix of traditional marketing tactics including:-
  • event marketing/corporate sponsorship
  • special promotions
  • information, communications and skills development
  • advertising
  • direct marketing
  • public health/media relationships
Such social marketing campaigns have been used in Canada since 1985/6. The impact has been monitored and the report [2] gives information up to 1992.

Does it work?

The graph shows considerable reductions in the use of alcohol, tobacco and drugs by teenagers aged 11-17 between the years 1989 and 1992.
It is not possible to ascribe all, or indeed, any, of this fall to social marketing since there would have been many different influences on behaviour. However, this report is worth reading, despite an apparent lack of evidence, if only because of the way that it profiles different teenagers and examined what methods are likely to influence target groups with completely different attitudes to drugs. Well worth a read, especially for those engaged in preventative health campaigns.


  1. GJ Botvin, E Baker, L Dusenbury, EM Botvin, T Diaz. Long-term follow-up of a randomized drug abuse prevention trial in a white middle-class population. Journal of the American Medical Association 1995 273 : 1106-12.
  2. Making a Difference II. The impact of the Health Promotion Directorate's social marketing campaigns 1991-1992. Available from Canada by faxing (613) 990-7097. Également disponsible en français.

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