WASHINGTON (AP) — A massive advertising campaign is part of the Trump administration’s plan to attack America’s opioid crisis. Yet an AP Fact Check finds that such campaigns in the past have failed to have a strong impact on drug use among the young.

President Donald Trump is focusing on advertising to discourage young people from trying drugs. In declaring opioid overdoses a public health emergency, the president said he thinks “really tough, really big, really great advertising” will become “the most important thing.”

Yet government and academic assessments of “Just Say No”-style messages have repeatedly shown poor results. A study funded by the National Institutes of Health found a nearly $1 billion national campaign designed to discourage use of illegal drugs among young people had no favorable effects on their behavior.