A generation unstained by nicotine – that's what Britain's prime minister says he wants to create. 

Rishi Sunak's proposed smoking ban would prevent children currently under 14 from ever taking a puff, while letting older people carry on as usual. The age-based approach has attracted controversy, but medical experts say there is a biological logic to treating teenagers differently. 

That's because nicotine affects the synapses – connections formed between brain cells every time a new memory is made or skill is learned – and adolescent brains build synapses much faster than adult ones. Nicotine hijacks this process, altering young brains, leaving them more prone to addiction. That vulnerability doesn't fade with age, so people who smoke as youngsters are more likely to struggle with other forms of addiction later in life.

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"What nicotine does to the brain – that is the hook that gets them into smoking in the long term," says Jacob George, Professor of Cardiovascular Medicine at the University of Dundee Medical School.

And life-long addiction isn't the only risk teenagers face. Nicotine can damage still-developing brains, harming areas responsible for impulse-control, attention, learning and mood. Research on animals at Yale University suggests that vaping during adolescence can lead to attention deficit hyperactivity disorder, or ADHD.

Vaping is blamed for the rise in the number of adolescents experimenting with nicotine. The proportion of children who've used e-cigarettes has jumped by around 50 percent over the last year, from one in 13 to one in nine.

"The biggest problem is marketing," George says. "We've got thousands of flavors, and when you're trying to entice people with unicorn and bubble gum flavors, there's really only one age group you are targeting."

Research shows that e-cigarettes are a gateway to smoking. Adolescents who vape are almost four times more likely to end up using "combustible" cigarettes later, which contain about 8,000 different compounds, including tar and metals. George says these are extremely harmful to the young, developing blood vessels.

"If you get people hooked earlier, they are more likely to be hooked longer and have greater (cardiovascular) damage as early as their twenties and thirties."

George describes the proposed smoking ban as a good step towards a healthier future, but worries that existing smokers could be left behind.

"We should not be letting our guard down about stopping people from smoking cigarettes now. We should continue trying to reduce the smoking of cigarettes."

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