Researchers have long investigated the relationship between smoking and depression. It has been established that smokers are more likely to be depressed than non smokers, although some smokers claim that smoking has an anti-depressant quality. However recent research has claimed a causal link between smoking and depression. Researchers from the University of Otago in New Zealand sampled a population of 1000 men and women. They found that smokers had more than twice the prevalence of depression than non smokers. They concluded that nicotine addiction led to increased risk of depression. Professor David Fergusson, who led the research, said, “The reasons for this relationship are not clear. However, it’s possible that nicotine causes changes to neurotransmitter activity in the brain, leading to an increased risk of depression.” But he added that the study “should be viewed as suggestive rather than definitive.” There tends to be a belief among smokers who have been or who are depressed that smoking is a mood lifter. Research suggests this is not the case. It is more likely to be a case of expectation leading experience. In reality cigarette smoking seems to lower mood overall, and as this research seems to suggest even cause depression in some people.