There are many reasons why smoking tobacco is bad, but now researchers have found yet another reason why people should not smoke. A study found that smoking tobacco increases the risk of mental illness.
Researchers from the University of Bristol Tobacco and Alcohol Research Group (TARG), in collaboration with Bristol’s MRC Integrative Epidemiology Unit (IEU) and the NIHR Bristol Biomedical Research Centre (BRC), used UK Biobank data from over 450,000 individuals of European descent, of which 8% currently smoke and 22% are ex-smokers.
The team applied a diagnostic approach called Mendelian randomization. This method uses genetic variants associated with exposure, such as smoking, to support conclusions about cause-and-effect relationships. They found evidence that smoking tobacco increased the risk of depression and schizophrenia, while depression and schizophrenia also increase the chances of a person becoming addicted to nicotine.
Senior author of the study, Marcus Munafò, explained:
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. What this shows is that genetic studies can tell us as much about environmental influences, as about underlying biology.
The evidence adds to a growing body of work, suggesting that smoking can have opposing effects on mental health. The same team, in collaboration with the University of Amsterdam, published a study in the British Journal of Psychiatry that showed evidence that smoking tobacco increases the risk of bipolar disorder.
The study’s lead author, Dr. Robyn Wootton, said:
Individuals with mental illness are often overlooked in our efforts to reduce smoking prevalence, leading to health inequalities. Our work shows that we should be making every effort to prevent smoking initiation and encourage smoking cessation because of the consequences of mental health as well as physical health.
In 2016, the UK government’s mental task force made recommendations in its review that psychiatric hospitals should be smoke-free by 2018. Now, this new evidence adds more reason to support the application of smoke-free policies. The evidence not only shows that smoking can be harmful to mental health, but smoking is responsible for much of the excess mortality associated with mental illness.
