Only 3 to 5 percent of smokers studied in Greece have been able to kick the habit without any form of medical assistance, according to data released yesterday. At a medical conference held in Thessaloniki yesterday on heart disease, academics showed that most smokers use nicotine substitutes such as patches or chewing gum or take the drug bupropion. Bupropion (also called Zyban) is an anti-depressant primarily used to get people to stop smoking by affecting chemicals in the brain related to nicotine craving. According to a two-year study held by the Aristotle University of Thessaloniki on 220 smokers, about 40 percent who attempted to quit were able to do so by using bupropion. The survey found that about 82 percent of those surveyed were heavily addicted to nicotine.