Smoking increases risk of depression

New University of Otago, Christchurch, research published today in the prestigious British Journal of Psychiatry suggests smoking could increase the risk of depression.

The study was done by researchers from the University of Otago’s long-running Christchurch Health & Development Study.

It found people who were dependent on nicotine were more than twice as likely to have symptoms of depression as those who were not nicotine dependent.

The study involved more than 1000 people, who were asked at ages 18, 21 and 25, about their smoking habits and whether they had symptoms of depression.

Sophisticated statistical analysis of results found smoking increases the risk of developing depressive symptoms, rather than people being more likely to smoke because they are depressed.

Lead researcher Professor David Fergusson says “our findings are consistent with the conclusion that there is a cause and effect relationship between smoking and depression, in which cigarette smoking increases the risk of developing symptoms of depression.’’

“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.’’

Professor Fergusson emphasises the study does not prove smoking causes depression but rather increases a person’s risk.

The study was funded by the Health Research Council of New Zealand.