Smoking can be detrimental to mental health, but much of the excess mortality associated with depression is due to smoking
Researchers have found that tobacco smoking may increase the risk of developing depression and schizophrenia.
"Individuals with mental illness are often overlooked in our efforts to reduce smoking prevalence, leading to health inequalities," said study lead author Robyn Wootton from the University of Bristol.
"Our work shows that we should be making every effort to prevent smoking initiation and encourage smoking cessation because of the consequences to mental health as well as physical health," Wootton added.
For the study, published in the journal Psychological Medicine, the research team used UK Biobank data from 462,690 individuals of European ancestry, comprising 8 percent current smokers and 22 percent former smokers.
The team applied an analytic approach called Mendelian randomization, which uses genetic variants associated with an exposure (e.g. smoking) to support stronger conclusions about cause-and-effect relationships.
"The increasing availability of genetic data in large studies, together with the identification of genetic variants associated with a range of behaviors and health outcomes, is transforming our ability to use techniques such as Mendelian randomization to understand causal pathways," said study senior author Marcus Munafo.
"What this shows is that genetic studies can tell us as much about environmental influences - in this case, the effects of smoking on mental health - as about underlying biology," Munafo added.
The research also suggests that smoking can have adverse effects on mental health.
This new evidence adds further weight to support the implementation of smoke-free policies.
Not only is there evidence that smoking can be detrimental to mental health, but much of the excess mortality associated with depression is due to smoking, the study added.