German study reveals link between smoking and depression

German study reveals link between smoking and depression
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A large-scale German study has identified a clear association between smoking and depression, finding that current and former smokers are more likely to experience depressive disorders than people who have never smoked.

The research was conducted by a team led by the Central Institute of Mental Health (CIMH) in Mannheim as part of the German National Cohort (NAKO), the country’s largest population-based study. Researchers analyzed data from 173,890 participants aged 19 to 72, with women accounting for half of the sample.

Data were collected through face-to-face interviews and standardized questionnaires covering depression diagnoses, current symptoms, living conditions, and smoking habits. Participants were classified into three groups: 81,775 never-smokers, 58,004 former smokers, and 34,111 current smokers. Information on age at smoking initiation, daily cigarette consumption, and time since quitting was also recorded.

The findings showed higher rates of depression among current and former smokers, particularly among individuals aged 40 to 59. A dose–response relationship was observed, with depressive symptoms increasing alongside the number of cigarettes smoked per day. Starting smoking later in life was linked to a later onset of depression, while longer periods of smoking cessation were associated with more time since the last depressive episode.

Researchers noted that smoking is the leading preventable cause of premature death worldwide, responsible for more than eight million deaths annually, and emphasized prevention and cessation to improve mental health. They cautioned, however, that the study’s cross-sectional design does not allow for definitive causal conclusions.