The tendency of subjects with mental illness to use substances has been extensively discussed. A traditional hypothesis was that substance use is a means of self-medicating and dependence is therefore ‘caused’ by mental illness. On the contrary, data have been published that smoking precedes the diagnosis of mental illness and may contribute to the disorder. For example, there is an increased risk of first onset major depression in smokers53–56 and an increase in depressive symptoms in persons who smoked in adolescence.57–59 Ex-smokers do not differ from current smokers in their risk for mood disorders, although daily smoking may be a causal factor in panic disorder and agoraphobia.60 One interpretation of these data is that smoking confers additional risk in the development of psychiatric disorders.
