Oct. 15, 2008— -- Despite investing $1 billion in a massive anti-drug campaign, a controversial new study suggests that the push has failed to help the United States win the war on drugs.
A congressionally mandated study released today concluded that the National Youth Anti-Drug Media Campaign launched in the late 1990s to encourage young people to stay away from drugs "is unlikely to have had favorable effects on youths."
In fact, the study's authors assert that anti-drug ads may have unwittingly delivered the message that other kids were doing drugs, inadvertently slowing measured progress that was being made to curb marijuana use among teenagers.
"Youths who saw the campaign ads took from them the message that their peers were using marijuana," the report suggests as a possible reason for its findings. "In turn, those who came to believe that their peers were using marijuana were more likely to initiate use themselves."
The study's authors called the findings, published in the December edition of the American Journal of Public Health, "particularly worrisome because they were unexpected."
The widespread anti-drug campaign, which sprang from the efforts of The Partnership for a Drug-Free America and supervised by the White House Office of National Drug Control Policy, targeted 12- to 18-year-olds starting in 1998. It has since pervaded American households via commercials, Web sites, advertisements in movie theaters and other platforms.
According to the study, 94 percent of young people surveyed reported being exposed to the government campaign, on average seeing about two to three messages per week.
"Overall, the campaign was successful in achieving a high level of exposure to its messages; however, there is no evidence to support the claim that this exposure affected youths' marijuana use as desired," the report said.
This afternoon, the White House Office of National Drug Control Policy disputed the study's findings. ONDCP spokesman Tom Riley said the ads in the study concluded four years ago, and since that time, the anti-drug campaign has significantly evolved, in part to incorporate new research into its messages.
"This campaign has been a striking success," Riley said. "Teen drug use in exactly the campaign's demographic has dropped sharply - there are over 800,000 fewer American teens using drugs now than there were in 2001."
The ONDCP also said evidence shows drug use among those not targeted by the campaign showed no change at the same time that behaviors changed specifically among those targeted. Riley said that in the same period of time, teens have become increasingly aware of the harm drugs can do.
Indeed, despite the study's findings, marijuana use among teens is down, not up.
Teenagers' marijuana use has declined by about 40 percent between 1997 -- before the anti-drug campaign began -- and 2007, according to a study released last year by the group, Monitoring the Future.
"Since the recent peak years of use reached in the mid-1990s, annual prevalence has fallen by over 40 percent among eighth-graders, 30 percent among 10th-graders, and nearly 20 percent among 12th-graders," the Monitoring the Future study found.
Lloyd Johnston, principal investigator for the Monitoring the Future study, told ABC News that if the government's ad campaign has not worked, there's something else out there driving down teen marijuana use. Johnston also said there is evidence that other government anti-drug messages have worked, adding that efforts to curb use of inhalants and ecstasy were followed by a drop in use of the drugs.
Johnston speculated that, assuming the anti-drug campaigns really were ineffectual, it may have been because the government "picked a hard target" by trying to demonize marijuana at the very time there was a competing push to legitimize medical marijuana.
Still, the recent report concluded the campaign was ineffective in changing behaviors.
Today, study author and professor at University of Pennsylvania's Annenberg School for Communication, Robert Hornik, told ABCNews.com that the reported decline in marijuana use "could be due to lots of influences, not just the campaign." He said he was expecting to conclude that the anti-drug campaign had positive effects, "but we couldn't find 'em."
"Despite extensive funding, governmental agency support, the employment of professional advertising and public relations firms, and consultation with subject-matter experts, the evidence from the evaluation suggests that the National Youth Anti-Drug Media Campaign had no favorable effects on youths' behavior and that it may even have had an unintended and undesirable effect on drug cognitions and use," the report said.
In other words, teens who specifically said they had a lot of exposure to the campaign messages were no less likely to stay away from marijuana than those who did not.
There is also a small amount of evidence that indicates the anti-drug campaign may have had the opposite effect for some teens. In one part of the analysis, teens who recalled seeing 12 or more anti-drug messages per month were actually more likely to start using marijuana than those who had seen fewer anti-drug messages per month.
The evaluation was conducted by the University of Pennsylvania's Annenberg School for Communication, after Congress called for the study. The study was based on four rounds of interviews conducted between 1999 and 2004, each involving about 5,000 to 8,000 youths between the ages of 9 and 18 years.
ABC News' Brian Hartman contributed to this report.