Everyone's different, but about three cigarettes in a few hours is all it takes to become dependent (addicted) and after that, staying dependent takes very little. Smokers who smoke more than five a day are probably dependent.

The reason is that nicotine is probably the most addictive substance that we know of. By itself, nicotine is a relatively safe drug, a bit like caffeine (which is mildly addictive) and it may have some value for treating a number of illnesses. The real problem is with the way nicotine gets into your system.

The rest of the chemicals and microscopic solids in tobacco smoke kill people. More people die from the effects of tobacco smoke than from all other drugs combined. In fact half of all smokers die as a result of tobacco smoking. Heart disease, emphysema, strokes, brain damage, blindness... the list goes on and on. Even light or "social" smokers suffer health problems as a result of their habit.

One of the biggest myths is that a smoke calms your nerves and helps you concentrate. It doesn't. What happens is that smokers start to go into nicotine withdrawal about 90 minutes after a smoke. The early symptoms are restlessness, loss of concentration, edginess and mild anxiety. All a cigarette does is stop the withdrawal craving.

I could take up pages of the health problems caused by smoking, but you can find them anywhere. Instead, I will mention just two that you might miss. Firstly, tobacco interferes with a lot of medical drugs, so smokers often need bigger doses of their medication before it works properly, and bigger doses mean more side effects, which is bad. Secondly, there is a lot of evidence now to show that young people who smoke are more likely to suffer from depression and anxiety when they hit their 20s—it is looking more and more likely that smoking is the cause of that.

I suppose if death was all you had to worry about it would be different: everyone dies of something so why not tobacco? The sad thing is, it not only robs smokers of about 20 years of life (on average), but many of those last years are spent in illness and dependence on other people, as your family watches you die, slowly, in pain and without dignity. Sombre note to end on, but it's true.