Nicotine is much less harmful than the tobacco that naturally contains it. It has never been found to cause cancer. Nor does it cause other smokers’ diseases such as emphysema. But it is, of course, strongly linked with why smokers smoke at all. Beyond avoiding nicotine-induced withdrawal symptoms, such as irritability and anxiety, many say they smoke to “stay focused”. This has led scientists to consider whether nicotine might directly influence people’s ability to think.

In 2010 researchers at America’s National Institutes of Health pooled the results of 41 trials on nicotine’s cognitive effects. Participants were either given a placebo or nicotine (though a few used tobacco, not pure nicotine). They found that a nicotine hit had “significant positive effects” on attention and memory.

This mental sharpening arises because nicotine is a stimulant. It prods neurons to release brain chemicals called neurotransmitters, including dopamine, glutamate, noradrenaline and serotonin. These promote alertness, learning, memory and motor control. Brain-scan studies also show that nicotine’s stimulating properties increase blood flow to parts of the brain involved in thinking, such as the prefrontal cortex and the thalamus.

With such compelling evidence of benefits, it is tempting to think that nicotine or similar compounds might even be useful therapeutics. One study, published in Nature Medicine in 2017, described how nicotine reversed mental deficits in mice with a gene variant linked with schizophrenia in humans, opening the door to novel treatments. A review published in 2023 also found that nicotine improved both short- and long-term memory in people with Alzheimer’s and Parkinson’s diseases.

But this influence on brain chemistry has a worrisome side, too. It is possible that regular exposure during critical periods in development, namely in the womb or during adolescence, can rewire the brain in unfavourable ways. As it would be unethical to test these things rigorously in people, scientists look for insight in animal studies even if the findings are not directly transferable.

In one study on rats, researchers found that nicotine exposure during adolescence, but not adulthood, led the animals to be more impulsive later in life and show an inability to pay attention to visual stimuli. Another found that exposed adolescent rats later showed anxiety and depression-like behaviours. Similar outcomes have been found for mice exposed in the womb.

And nicotine really is addictive. The dopamine it stimulates, particularly in a brain area called the nucleus accumbens, activates the brain’s reward network by creating a pleasurable sensation which, when it fades, produces an urge to take nicotine again.

Among psychoactive drugs, this state of affairs is not unique. Alcohol and caffeine, for example, can also harm developing brains and yet provide some benefits to adults. Nicotine’s upside of a mental boost should similarly be considered in context—as downsides go, addiction is nothing to sniff at.■