Smoking Linked to Increased Risk of Depression and Bipolar Disorder, Study Reveals

We are familiar with the health hazards associated with smoking, from gruesome images on cigarette packs to the risk of various cancers. However, what many may not realize is that smoking is also linked to an elevated risk of mental illnesses.

In recent years, extensive research has suggested a strong connection between smoking and mental health issues. Yet, scientists have debated whether smoking directly causes these disorders or if people smoke to alleviate symptoms of underlying mental conditions.

Now, clarity emerges. Collaborating with Canadian colleagues, Doug Speed from Aarhus University’s Center for Quantitative Genetics and Genomics has provided evidence that smoking can indeed lead to depression and bipolar disorder.

“The numbers speak for themselves. Smoking does cause mental illness. Although it’s not the only cause, smoking increases the risk of being hospitalized with a mental illness by 250 per cent,” affirms Speed.

This revelation comes after analyzing a vast dataset of health information from over 350,000 individuals. To disentangle the complex web of factors contributing to mental disorders, researchers needed extensive data, and the UK Biobank provided just that.

The study found that people typically start smoking before the age of 20, while hospitalization for mental disorders tends to occur between ages 30 and 60. This temporal correlation strongly suggests that smoking precedes mental illness.

Genetics also play a role in smoking behavior, as the research indicates. Up to 90 percent of those in the dataset who smoked or had smoked began the habit before age 20. Genetic variants influenced this tendency to start smoking early, accounting for 43 percent of the risk.

Although the exact mechanisms linking smoking to mental illness are not fully understood, theories propose that nicotine may affect serotonin absorption in the brain, which is vital for regulating mood. Additionally, smoking could induce brain inflammation, potentially leading to various mental disorders.

Given the data showing that few people start smoking after age 20, raising the legal age for buying cigarettes could be a practical way to reduce smoking initiation and, consequently, lower the risk of mental illness. Further research, including Danish and Finnish data, is planned to confirm these findings.