You left out a significant group: addicted, unhappy about it, but unable to kick the habit. Which is most smokers I know who have smoked for more than a few ye

You left out a significant group: addicted, unhappy about it, but unable to kick the habit. Which is most smokers I know who have smoked for more than a few years, including myself. Smoking actually does have a lot of mental effects, either directly or indirectly. For one it has a marked effect on oxygen saturation which definitely can have cognitive effects. Nicotine itself is very short-lived, and can temporarily improve some cogntitive functions. But since the possibility of smoking is highly variable throughout a typical active day, this effectively leads to a sort of oscillation between short windows of increased cognitive function and decreased function due to beginning withdrawal.