Why is it so hard to quit smoking?

A bitesize explanation of how receptors in the brain lead to nicotine tolerance and then addiction

Astudy has found that 43% of women who give up smoking during pregnancy take it up again soon after they give birth. Why so many? It’s no surprise that nicotine is addictive, but what goes on in the brain during a cigarette craving?

Nicotine is picked up in the brain by ‘nicotinic’ receptors. We also have ‘cannabinoid’ and ‘opioid’ receptors which work in similar ways – there are no prizes for guessing what they pick up. These receptors didn’t evolve for humans to become addicted to drugs, but they happen to provide a more direct pathway for these plant-based chemicals to reach the brain. Over time, smokers adapt to the presence of nicotine and develop a tolerance, leading to cravings.

This means that nicotine addiction develops in a more fundamental, chemical way than addictions to sex, the internet or even chocolate. There are no ‘internetinoid’ or ‘chocolatinoid’ receptors in the brain – instead, dependencies develop through more indirect pathways related to reward and pleasure.

Not everyone who smokes becomes addicted, but as the women in the study will tell you, this chemical ‘hardwiring’ makes it very difficult to quit.

Photo credit: Deep breath: addiction develops in a more fundamental, chemical way than other addictions. Photograph: Jonathan Brady/PA

This article was first published on the Guardian website as part of the A neuroscientist explains series.