As if continuing a series of scary pictures from cigarette packages warning against the dangers of smoking, scientists at the University of Bristol have proven the relationship of nicotine addiction with the risk of developing schizophrenia and depression.
Science has already proven that people with mental disorders, especially those with depression and schizophrenia, smoke much more often than others. However, until now, researchers have not been able to determine for sure whether this is a causal relationship, and, if so, in what direction: whether mental illness increases the likelihood of smoking or whether smoking itself is a risk factor for mental disorder.
Researchers from the University Research Group of Bristol, with the support of the Center for Integrative Epidemiology and the Center for Biomedical Research, studied data from the British Biobank – 462 people of European origin, including 690% smokers and 8% ex-smokers.
The team applied an analytical approach – Mendelian randomization. The method uses genetic variants associated with various exposures (eg smoking) to test concepts of cause and effect. Through this approach, scientists have found evidence that, on the one hand, tobacco smoking increases the risk of depression and schizophrenia, and on the other hand, that these disorders increase the likelihood of smoking (although in the case of schizophrenia, the evidence is somewhat weaker).
Psychiatry and smoking
The same group of scientists, in collaboration with the University of Amsterdam, had previously concluded that tobacco smoking increased the risk of developing bipolar disorder.
Back in 2016, the UK government’s Mental Health Committee recommended that the country’s psychiatric hospitals be smoke-free. The new evidence gave the committee grounds for implementing a smoke-free policy. Modern science has all the evidence that this habit can be harmful to mental health, and also confirms the sad statistics: a significant percentage of deaths in patients with mental illness is associated with nicotine addiction.
Genetic studies can reveal a lot about the impact of smoking on a person’s mental health
“In the context of general efforts to reduce smoking prevalence, people with mental illness are often overlooked,” explains Dr. Robin Wootton, senior researcher at the School of Psychological Sciences and lead researcher. “Our work shows how important it is to make every effort to ensure that people do not start smoking or, after smoking, get rid of this habit, because its consequences for mental and physical health are huge.”
“Every day we have more genetic research data,” adds Markus Munafo, professor of biological psychology at the Bristol School of Psychological Sciences and senior project developer. “This gives ample opportunity to use new methods, such as Mendelian randomization. They, in turn, help in understanding cause and effect relationships. Genetic studies can reveal a lot about the impact of smoking on a person’s mental health.”
That is why in many countries the scientific conclusions of such studies form the basis of public health programs.