The relationship between cigarette smoking
and pulmonary and cardiovascular diseases is
well established Indeed, early reports on the
association of smoking and lung cancer were
the major impetus for public health efforts to
curb smoking. The publication in 1964 of the
surgeon general’s report on smoking and
health was associated with a steady decline in
smoking—a trend that in the following decades
likely contributed to declining rates of lung
cancer, especially among men.The relationship
between cigarette smoking and
mental disorders, however, remains less well
characterized.
Several large community surveys have
found increased prevalence of mental disorders
among smokers. Longitudinal studies
have shown an increased risk of subsequent
mood and anxiety disorders in individuals who
smoked cigarettes and suggested that the effects
might vary according to gender and
age. Although longitudinal studies can
establish the temporal order of smoking and
subsequent incidence of mental disorders, their
findings can be confounded by factors that
are not known or that are difficult to measure,
such as a common genetic predisposition
or a specific personality diathesis, and that
could explain the observed association of
smoking and mental disorders.
Establishing the causal link between smoking
and mental disorders conclusively would
require experimental evidence, which is generally
difficult or impossible to obtain. Exposing
research participants to tobacco products in
a randomized trial raises ethical issues. Controlled
randomized trials of smoking cessation
interventions might provide causal evidence.
However, nicotine withdrawal is often associated
with significant early psychological symptoms
that may overshadow mental health
benefits of smoking cessation. Furthermore,
randomized trials often comprise a highly selected
group of participants, and their findings
may not be generalizable.
Because of these limitations, prospective observational
studies of representative populationbased
samples may provide the best available
means to investigate the causal links between
smoking and common mood and anxiety disorders.
Confidence in causal inferences from such
data may be enhanced by the use of statistical
methods designed for such inference, such as
instrumental variable methods.
In this study, we examined the association
between smoking and subsequent development
of mood or anxiety disorders in data from the
longitudinal National Epidemiologic Survey on
Alcohol and Related Conditions (NESARC),
a large prospective epidemiological survey of the
US population.32---34 We examined the association
of regular smoking during at least part of the
3-year follow-up period with new onset of major
depressive episodes, dysthymia, manic episodes,
generalized anxiety disorder, panic disorder,
social phobia, specific phobias, and posttraumatic
stress disorder. Our hypothesis, derived from
previous researchwas that regular
smoking is associated with an increased
risk of new onset of these mood and anxiety
disorders. We also assessed the dose---response
relationship between the average number
of cigarettes smoked and the risk of newonset
disorders and whether the relationship
between smoking and new-onset
psychopathology varied by sociodemographic
characteristics.