Recent research suggests that smoking and depression might share a common aetiology, but little evidence regarding the mechanisms that influence this association is available.

Dr Lisa Dierker and colleagues from Wesleyan and Yale Universities in the US used family data to discriminate between causal and shared aetiologic mechanisms for the co-occurrence of smoking and depression.

The team studied 273 directly interviewed first-degree relatives and 133 of their probands who had attended outpatient substance-abuse or anxiety clinics. Information on tobacco use and depressive symptoms was collected.

A relative-risk regression model was used to estimate the risk ratios and their standard errors. Factors such as sex and psychiatric and substance-use disorder comorbidity was taken into account.

The pattern of cross-aggregation of heavy smoking and depression differed according to the subtype of depressive disorder – dysthymia and heavy smoking appeared to share a common aetiology while major and double depression did not demonstrate a shared vulnerability with heavy smoking.

The team said that investigations into the mechanisms of comorbidity have particularly important implications for prevention and treatment.

“If evidence for a direct or indirect causal link is established, intervention trials can be designed that focus on the primary prevention of the secondary condition,” said the study authors.

They concluded that further research into the association between smoking and depression is needed, focusing particularly on genetics and the environment.

Reference: Dierker et al, American Journal of Psychiatry 2002;159:947-953
© Health Media Ltd 2002
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