Khaberni - A wide-ranging German study has revealed a clear relationship between smoking and depression, confirming that current and former smokers are more susceptible to the disorder compared to those who have never smoked.
The study was conducted by a research group led by the Central Institute for Mental Health (CIMH) in Mannheim, within the framework of the German National Study (NAKO), which is the largest population study in Germany.
The researchers relied on analyzing data from 173,890 participants aged between 19 and 72 years, half of them women. Data were collected through personal interviews and standardized questionnaires including depression diagnoses, current symptoms, living conditions, and smoking habits.
Based on this data, participants were divided into three categories: 81,775 people who had never smoked, 58,004 former smokers, and 34,111 current smokers. The study also documented the age at which smoking began, the average number of cigarettes smoked per day, and the time elapsed since quitting smoking among former smokers.
The results showed that depression was more prevalent among current and former smokers compared to non-smokers, especially in the middle-aged group between 40 and 59 years, which suggests a potential role for temporal factors alongside social factors in impacting mental health.
The study also identified a clear dose-response relationship; the increase in the number of cigarettes smoked daily was associated with an increase in the severity of depression symptoms, at a rate of 0.05 additional symptoms per cigarette. Conversely, starting smoking at a later age was associated with a delayed onset of the first depressive episode.
The results also indicated that quitting smoking has tangible positive effects, as longer periods of quitting were associated with a longer duration since the last depressive episode.
The researchers noted that smoking is the leading preventable cause of early death globally, contributing to more than 8 million deaths annually, according to the World Health Organization, underscoring the importance of preventing smoking initiation and encouraging smokers to quit to improve mental health.
The research team pointed out that the cross-sectional design of the study and the reliance on retrospective data do not allow for definitive causal conclusions, confirming the need for future longitudinal studies that include genetic and imaging data to more accurately understand the mechanisms and potential causal relationships.
