New research published today in the British Journal of
suggests smoking could increase the risk of
study, carried out by researchers from the University of Otago
in New Zealand, followed over 1,000 people. At the ages of 18, 21
and 25, the participants were asked about their smoking habits and
whether they had symptoms of depression.
The researchers found a strong association
between smoking and depression. 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 researchers looked at this relationship in
more detail using a sophisticated statistical technique called
structural equation modelling (SEM). This analysis showed
that smoking increases the risk of developing depressive symptoms,
rather than people being more likely to smoke because they’re
Commenting on the results, lead researcher
Professor David Fergusson said: “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 and colleagues do
emphasise that their study does not prove that smoking causes
depression, and said that the study “should be viewed as suggestive
rather than definitive”.
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Boden JM, Fergusson DM and Horwood LJ (2010) Cigarette smoking and depression: tests of causal linkages using a longitudinal birth cohort, British Journal of Psychiatry, 196:440-446