Depressive symptoms implicated in lung cancer via smoking habits

Individuals with greater depressive symptoms are at risk of developing lung cancer, with the association directly and indirectly attributed to smoking habits, as reported in a study.

The study used data from the Nurses' Health Study and included a total of 42,913 women who completed measures of depressive symptoms, sociodemographics, and other factors including smoking in 1992.

Researchers assessed depressive symptoms at two time points: 1996 and 2000. They also collected data on regular antidepressant use and physician-diagnosed depression starting in 1996. Multivariable Cox regression models were to estimate potential association to lung cancer risk, which was evaluated until 2016.

A total of 1,009 cases of lung cancer were documented during the study period. Of note, the incidence was higher among women with the highest vs lowest level of depressive symptoms. Analyses confirmed that greater depressive symptoms carried a 25-percent greater risk of developing lung cancer (fully adjusted: hazard ratio [HR], 1.25, 95 percent confidence interval [CI], 1.04–1.51).

In mediation analyses, lifetime pack-years of smoking accounted for 38 percent of the overall association between depressive symptoms and lung cancer risk. Furthermore, when stratified by smoking status, the elevated lung cancer risk was evident among former smokers but not current or never smokers; however, the interaction term did not indicate any meaningful differences across groups (p=0.29).

Results were similar or stronger in an analysis that took into account time-updated depression status (using depressive symptoms, physician diagnosis, and regular antidepressant use) and chronicity of depressive symptoms.