A study shows that smoking increases the risk of developing depression by more than 100%.

VALENCIA (EP). Smoking increases the risk of depression by more than 100%, according to a new study from Aarhus University (Denmark), which at the same time adds that if you stop smoking, you can significantly reduce this risk.

Most people know that tobacco smoking is unhealthy and can cause all types of cancer, but many probably don’t know that it also increases the risk of mental illness.

In recent years, more and more studies point to a strong correlation between smoking and mental illness. However, researchers have not been able to agree on whether smoking causes depression or other mental disorders, or whether we smoke because we need to relieve the symptoms of an underlying mental disorder.

Together with two colleagues from Canada, Doug Speed, from the Center for Quantitative Genetics and Genomics at Aarhus University, showed that smoking can cause depression and bipolar disorder. “The numbers speak for themselves. Smoking causes mental illness. Although it’s not the only cause, smoking increases the risk of hospitalization for mental illness by 250%,” he says.

“Smoking often precedes mental illness. In fact, much earlier. On average, people in the dataset started smoking at 17, while they weren’t usually hospitalized with a mental disorder until their 30s,” he says.

Before Doug Speed ​​and his colleagues could answer whether smoking can cause mental disorders, they needed very large amounts of data. There can be many different reasons why we develop a mental disorder, so it was important that they had enough data to clear their numbers of other possible consequences.

To do this, in a study published in the journal Acta Psychiatrica Scandinavica, they turned to the British Biobank, one of the world’s largest databases of human health information. The database contains the genetic data of more than half a million people. The genetic data was combined with a large amount of other medical information and with the participants’ answers about their lifestyle.

They entered the data into a computer and started looking for patterns, using a new way of looking for correlations between smoking and mental illness that hadn’t been used before. “Previous research hasn’t really taken into account the fact that there might be a time dimension here,” he explains. Fine”. we are on average 30 to 60 years old.”

“Smoking usually precedes mental illness. In fact, much earlier,” he says. “On average, people in the data set started smoking at 17 years old, while they were not usually hospitalized for mental illness.” thirty”.

Up to 90% of the people in the dataset who still smoked or were smokers started smoking before the age of 20. Therefore, the likelihood that you will then start smoking is very small. In fact, your genes help determine whether you become a smoker, explains Doug Speed.

“When we looked at many smokers in the database, we found a number of recurring genetic variants,” he continues. “Looking at twin studies in which twins had the same genes but grew up in different homes, we could see that their genes could explain 43 % risk of becoming a smoker.

In families where adoptive parents also smoked, the risk that the child would begin to smoke increased. However, if the parents did not smoke, the risk was lower, but it was still higher when the children’s “real” parents were smokers and passed on certain genes.

“There are a number of genetic variants that we might call “smoking-related genes.” People in the dataset who carried smoking-related genes but were non-smokers were less likely to develop psychiatric disorders compared to those who carried those genes. “And they smoked,” he says. “Because genetic variants are also associated with the risk of mental illness, it used to be a little confusing. But in this study, we showed that the risk of starting smoking probably increases the risk of developing mental disorders due to “ genes associated with smoking.

According to statistics, smoking causes mental disorders such as depression, bipolar disorder and schizophrenia. However, Doug Speed ​​and his colleagues have no explanation why, there are only a number of theories. “We have yet to find the biological mechanism that causes smoking to cause psychiatric disorders. One theory is that nicotine inhibits the uptake of the neurotransmitter serotonin in the brain, and we know that people with depression don’t produce enough serotonin,” he explains.

When one cigarette is smoked, nicotine triggers the production of serotonin in the brain. Among other things, this is what makes you feel relaxed after smoking. But if you continue to smoke, nicotine will have the opposite effect. Instead, it will suppress serotonin, which can lead to anxiety, malaise, and instability.

“Another explanation could be that smoking causes inflammation in the brain, which in the long run can damage parts of the brain and lead to various mental disorders. But like I said, we don’t know for sure yet,” he admits.

The new figures show that we rarely start smoking after 20 years of age. Therefore, it would be a good idea to study whether it is worth raising the age limit for buying cigarettes.

“It could be a good way to prevent smoking. Again, we don’t know why people don’t start smoking in their 20s, but it could be because we’re less willing to take risks as we age.” suggests Doug Speed: “So changing the law and raising the age limit could have an effect. At least there are signs of it.”

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