According to the researchers, data shows that smoking doubles the risk of depression, schizophrenia and bipolar disorder.
“The numbers are very clear. Smoking is a cause of mental illness. It is not the only cause, but it increases the chance of hospitalization for mental illness by 250 percent,” says Professor Doug Speed of the Center for Quantitative Genetics and Genomics at Aarhus University.
Researchers have disagreed about causation: Do we get depression or other mental illnesses because of smoking? Or do we smoke because we need to suppress an underlying mental illness?
But the new research confirms that smoking often precedes the development of mental illness.
So smoking usually precedes mental illness. It starts much earlier. On average, people in the data set started smoking at age 17, while most were admitted with a mental illness at age 30.
Researchers do not have an exact explanation for why smoking increases the risk of mental illness.
“We haven’t yet found the biological mechanism by which smoking leads to mental illness. One theory is that nicotine blocks the reuptake of the neurotransmitter serotonin. We know that people with depression don’t produce enough serotonin,” says Doug-Speed.
When you smoke a single cigarette, nicotine stimulates the production of serotonin in the brain. This can provide a relaxing effect.
However, if you continue to smoke, nicotine may have the opposite effect and start to dampen serotonin production instead.
The researchers said this can make you anxious, sad and uneasy.
According to the Trimpus Institute, almost one in five Dutch smokers.
