I leave you a summary
Some studies have shown that nicotine in cigarettes increases concentration and attention (which makes smokers feel more alert), but cigarettes contain many other substances. 4,000 chemicals in total, of which 50 are toxic by nature: the carbon monoxide that derives from the smoke expelled by cars, butane, and arsenic, ammonia and methanol in the gasoline of rockets, for example. It is believed that the long-term accumulation of these toxic chemicals can damage the brain, which would generate deficits in learning and memory, essential for daily tasks such as remembering a medical appointment or taking medicine on time. They also affect the executive function, which is the one that helps us plan tasks, pay attention and ignore distractions. Without them daily life would be much more difficult.