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Smoking is bad for you and you shouldn’t do it. You know both of these things, of course: you’ve been told them in school, on TV and the radio, by doctors, and via the Cronenbergian body-horror of cigarette packets themselves. It’s worth reiterating, though, for two reasons: first, because the effects of having a quick puff outside the pub aren’t just a long-term gamble on your health but an immediate way of making your life worse; and second, because cigarettes remain wildly, impossibly addictive. Some research suggests that as many as two-thirds of people who try one cigarette become, at least temporarily, daily smokers, while a recent survey found that less than a fifth of UK smokers trying to quit actually managed it. Estimates for the average number of times people try to quit before actually managing it range from half a dozen to well over a hundred. So what confluence of factors actually makes cigarettes so difficult to give up – and what does that mean for a wannabe quitter?
“The first thing that happens when you smoke a cigarette is that you inhale a noxious mix of nicotine, various irritants and carcinogens into your lungs, ‘stunning’ your cilia – the tiny, hair-like projections that line your airways – and making them do their job less effectively,” says Lion Shahab, professor of health psychology at University College London. “The other thing that happens very, very quickly is that nicotine gets absorbed through the lungs into the alveoli, into the bloodstream, and then gets transferred into the brain. This is when you start to feel good, and also a key thing that keeps you addicted.”
Essentially, nicotine taps into your brain’s reward pathways and starts to release dopamine and serotonin within about 10 to 20 seconds of your first inhale, giving you the “pleasure” response associated with smoking very rapidly. (“If it took a couple of hours for that dopamine release, people probably wouldn’t get addicted,” says Professor Shahab.) At the same time, nicotine “unlocks” your adrenal glands, pouring epinephrine (adrenaline) and norepinephrine (another hormone vital for the “fight-or-flight” stress response) into your bloodstream and giving you a brief buzz. Nicotine levels in the blood peak after about 20 minutes, and then it’s all downhill.
“With smoking, withdrawal symptoms kick in very quickly, as the half-life – the amount of time it takes for your body to metabolise and eliminate 50% of it – of nicotine is about two hours,” says Professor Shahab. “At the same time, most smokers have dopamine receptors that have slowly become desensitised. So you’ve got this expectation of dopamine being released, you don’t get that much, and the feeling of satisfaction goes away very quickly. The interesting thing is that people often claim they feel better when they have a cigarette, but that’s a misunderstanding of what happens. Smoking basically brings you back to the baseline level you should have been at if you’d never smoked in the first place.”
One key consequence of this is that smoking often has a profound impact on mental health, because you’re essentially in constant withdrawal if you don’t have a cigarette in your hand. The relationship between smoking and anxiety and depression is complicated, because it’s bidirectional – meaning that people who have these issues can be more likely to start smoking – but at least one large-scale review suggests that if you do stop smoking, your mental health can measurably improve in a pretty short space of time.
There are, of course, dozens of other downsides to smoking. In short: worse reproductive health; worse oral health; higher risk of conditions such as stroke, heart attack, type 2 diabetes or pneumonia; worse bone and immune system health; accelerated ageing and cognitive decline. Your red blood cells “prefer” the carbon monoxide in smoke to oxygen, meaning that there’s less of the latter being carried through your tissues: in the short term, this can mean shortness of breath, but over the long term it puts strain on your heart. Your blood vessels stiffen and the lining of the arteries becomes damaged, making it easier for fatty plaques to build up. Your cilia die (though they can recover, to some extent).
And, of course, there’s the big one.
“You never know what level of smoking will cause DNA damage that can’t be repaired and therefore causes cancer,” says Shahab. “You can think of it like a big game of Russian roulette – some people can smoke for 50 years, and it’s the 200,000th cigarette that gets them.” For others, the damage starts much, much earlier. “It’s a bell curve, but we have studies which show very clearly that on average, a smoker dies 10 years earlier than a non-smoker, and that smokers get the diseases of old age earlier.”
The good news is that many of these things are reversible: aesthetic improvements happen very quickly, while the rest of your health can recover markedly over time. But for any of that to happen, you have to give up. And, for all the reasons discussed above, it’s not easy. So what does the science of addiction say about quitting?
Well, according to a 2023 Cochrane review, you’re least likely to do it if you go cold turkey: on average, for every 100 people trying to quit, six are likely to manage without using any aids. Nicotine patches, which slow the delivery of the drug (and thus its addictive spike) are slightly better: about nine people in 100 successfully quit with them, a number that goes up to 12 if they’re used in tandem with other aids.
That leaves e-cigarettes/vapes and the prescription medicines varenicline and cytisine as the most evidence-backed aids. The former are effective as they allow you to maintain the ritual of a “smoke break” without tobacco’s carbon monoxide and tar, but they can be difficult to quit themselves. Varenicline and cytisine are partial agonists – they bind to the receptors in the brain that nicotine usually latches on to, and also cause the release of dopamine and serotonin so you don’t have as many withdrawal symptoms. But there’s a second layer to their effects: when you then smoke a cigarette, you don’t get any rewarding effect, because your nicotine receptors are occupied. You’re in effect breaking the psychological link between habit and “pleasure”. But, according to the studies, you’ve still only got a 14% chance of success.
“Smoking is very, very addictive – more so than heroin or cocaine by some measures,” says Shahab. “Don’t give up on giving up. Allow yourself to fail and try again.” And remember: everyone loves a quitter.
