Governments spend millions warning kids not to do drugs, but a new study suggests that dropping out of high school in the US could be just as deadly as smoking.

After analysing data going back to 1925, researchers from the University of Colorado Denver calculated that 145,000 deaths in the US could have been prevented in 2010 if adults who didn't finish high school had graduated. That's comparable to the estimated number of lives that could have been saved if all the smokers in the country had quit.

The team also calculated that another 110,000 deaths in 2010 could have been prevented if college dropouts had finished their degrees. 

"Our results suggest that policies and interventions that improve educational attainment could substantially improve survival in the US population, especially given widening educational disparities," co-author Patrick Krueger said in a press release. "Unless these trends change, the mortality attributable to low education will continue to increase in the future."

While the study doesn't suggest that there's direct causal link between not finishing school and mortality risk, it relied on well-established health risks associated with low education. Things like earning less, poorer mental wellbeing, and being less likely to adopt healthy behaviours such as eating well and exercising regularly have all been associated with low education in previous studies.

And even though the mortality rates are estimates, the researchers came up with their numbers in the same way that scientists calculate the risk of smoking, which makes the two figures comparable. To do this, they first analysed the mortality rates and education levels of more than 1 million people in the US, and then applied these rates to different populations.

Of course, nobody's suggesting that being better educated will stop people getting sick or dying, but it can help equip people to make healthier choices throughout their lives. Bottom line? "Paying attention to education has the potential to substantively reduce mortality," said co-author Virginia Chang.

It's currently estimated that more than 10 percent of the US population aged between 25 and 34 haven't finished high school, and another 28.5 percent haven't completed a college degree. While the researchers accept that not everyone has the desire to do further education, they believe it should be a goal to get everyone to finish high school.

"In public health policy, we often focus on changing health behaviours such as diet, smoking, and drinking," said Chang. "Education - which is a more fundamental, upstream driver of health behaviours and disparities - should also be a key element of US health policy." 

The study has been published in the journal PLOS ONE.