A research group led by the Central Institute of Mental Health (CIMH) in Mannheim, Germany, has confirmed an association between cigarette smoking and depression using data from the German National Cohort (NAKO).

The study, published in ‘BMC Public Health’, found that depression occurs more frequently over the lifetime of current and former smokers than among people who have never smoked.

It also identified clear dose-dependent effects, showing that the more cigarettes smoked, the higher the risk and severity of depressive symptoms. “With over eight million smoking-related deaths worldwide, smoking is the leading preventable cause of premature mortality,” according to World Health Organisation data from 2021.

While the link between smoking and depression has long been suspected, lead researchers said the underlying mechanisms remain unclear.

“Although the association between smoking and depression is well established, the mechanisms underlying this link remain poorly understood,” said Maja Völker, a doctoral candidate at CIMH. “We therefore examined dose-response relationships and time factors such as age at onset and time since smoking abstinence.”