A large new study in Germany has confirmed that people who smoke or have smoked in the past are more likely to experience depression than those who never smoked.
This important research comes from the Central Institute of Mental Health (CIMH) in Mannheim and uses data from the German National Cohort, the largest population study in Germany. The results were published in the journal BMC Public Health.
Researchers found that the risk of depression increases with the number of cigarettes a person smokes. The study also showed that quitting smoking can reduce this risk over time—the longer someone stays smoke-free, the lower their risk of depression becomes.
Smoking is already known to be the top preventable cause of early death around the world, with more than 8 million deaths each year according to the World Health Organization. But while experts have long believed there’s a connection between smoking and depression, the exact reasons behind this link are still unclear.
That’s why this new study focused on how smoking habits—like how many cigarettes are smoked each day and how long someone has been smoke-free—might affect the risk of depression.
The study included nearly 174,000 people, ages 19 to 72, with half of them being women. Participants were divided into three groups: those who never smoked (about 82,000), those who used to smoke (58,000), and those who still smoked (34,000).
They answered questions about whether they had been diagnosed with depression, if they currently had symptoms, and details about their smoking history, including how old they were when they started and how many cigarettes they smoked each day.
The results showed that both current and former smokers had higher rates of depression during their lifetime compared to people who never smoked. This was especially true for people aged 40 to 59. It suggests that the link between smoking and depression could change with age, and that both social and time-related factors may play a role.
A clear pattern also appeared: the more someone smoked, the more depressive symptoms they reported. In other words, higher cigarette use was tied to worse mental health. People who started smoking later in life also experienced their first episode of depression later, suggesting some connection between the timing of smoking and mental health problems.
The good news is that quitting smoking helps. People who had quit smoking many years ago had gone longer without a depressive episode compared to those who quit more recently. This shows that stopping smoking can be a step toward better mental health.
The researchers did not include other tobacco products, like cigars or pipes, in this study. Also, because this was a cross-sectional study (a snapshot in time), it can’t prove that smoking causes depression. However, the strong connections found suggest that smoking and depression are linked in important ways.
Dr. Fabian Streit from CIMH said the findings highlight the need to prevent people from starting to smoke and to support those who want to quit.
He also emphasized how important it is to understand how much a person smokes, since heavier smoking is linked to more serious depression. In contrast, staying away from cigarettes for a long time seems to improve mental well-being.
Future studies that follow people over time and include genetic and brain imaging data may help explain exactly how smoking affects mental health.
If you care about mental health, please read studies about how dairy foods may influence depression risk, and 6 foods you can eat to improve mental health.
For more mental health information, please see recent studies about top foods to tame your stress, and Omega-3 fats may help reduce depression.
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