Source: Thailand Medical News Nov 15, 2019 5 years, 1 week, 1 hour, 45 minutes ago
Researchers from the University of Bristol, in a new study, has found that tobacco
smoking increases the risk of developing
depression and
schizophrenia.
It is known that
smoking is much more common amongst people with mental illness especially
depression and
schizophrenia. However, most studies that have looked at this association have not been able to disentangle whether this is a cause-and-effect relationship, and if so in which direction. Does mental illness increase the likelihood of
smoking, or is
smoking itself a risk factor for mental illness?
Medical researchers from the University's Tobacco and Alcohol Research Group (TARG) with support from Bristol's MRC Integrative Epidemiology Unit (IEU) and the NIHR Bristol Biomedical Research Centre (BRC), used UK Biobank data from 462,690 individuals of European ancestry, comprising 8 per cent current smokers and 22 per cent former smokers.
The research team applied an analytic approach called Mendelian randomisation, which uses genetic variants associated with an exposure (e.g.
smoking) to support stronger conclusions about cause-and-effect relationships. They found evidence that tobacco
smoking increased risk of
depression and
schizophrenia, but also that
depression and
schizophrenia increase the likelihood of
smoking (although the evidence was weaker in this direction for
schizophrenia).
The new study adds to a growing body of work suggesting that
smoking can have adverse effects on mental health. The same group published a similar study in
British Journal of Psychiatry earlier this year in collaboration with the University of Amsterdam, showing evidence that tobacco
smoking increases the risk of bipolar disorder.
The British government's mental health task force made the recommendation in their 2016 review that psychiatric hospitals should be smoke free by 2018. This new evidence adds further weight to support the implementation of smoke-free policies. Not only is there evidence that
smoking can be detrimental for mental health, but much of the excess mortality associated with mental illness is due to
smoking.
"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 to mental health as well as physical health." commented Dr. Robyn Wootton, Senior Research Associate in the School of Experimental Psychology and the study's lead author, in a phone interview with
Thailand Medical News.
"The increasing availability of genetic data in large studies, together with the identification
of genetic variants associated with a range of behaviours and health outcomes, is transforming our ability to use techniques such as Mendelian randomisation to understand causal pathways. 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." Commented Dr Marcus Munafò, Professor of Biological Psychology in Bristol's School of Psychological Science and senior author on the study.
Reference: "Evidence for causal effects of lifetime smoking on risk for depression and
schizophrenia: A Mendelian randomisation study" by Robyn Wotton, Marcus Munafò et al in
Psychological Medicine
