Smoking, a risk factor for suicide and suicidal behavior

A meta-analysis estimates that suicide mortality would be twice as high among smokers; it would even be 2.5 times higher among female smokers. So many reasons that invite us to consider including items on smoking in suicide risk assessment scales.

While the correlation between smoking and suicidal actions has already been highlighted, the correlation between smoking and suicidal behavior (ideation, planning, suicide attempts) is less well documented. In order to address this lack of data, a Spanish team has just published a meta-analysis on the relationships between smoking and suicide, including suicidal behavior.

Mortality risk doubled among smokers

The Spanish meta-analysis is based on the study of twenty scientific publications, selected from a database of 2,436 publications on this subject. In total, it is based on cohort studies involving 2,457,864 participants, allowing robust data to be obtained[1].

The results show a risk of suicide mortality multiplied by two for smokers as a whole, compared with that of non-smokers. This risk is increased to 2.5 for female smokers, who thus display a higher score than men, whereas, according to a "gender paradox", men (especially single men) are usually the people who die most by suicide. Ex-smokers, for their part, display a mortality rate 31% higher than that of non-smokers, but significantly lower than that of smokers. Suicidal thoughts are for their part 84% higher among smokers and 35% higher among ex-smokers, compared with non-smokers.

The authors conclude that smoking can be considered a risk factor contributing to suicide and suicidal behavior, even if it is far from being the only one. They suggest introducing smoking among the items of suicide risk assessment scales, particularly within the "SAD PERSONS" scale, which seems the most appropriate to assess this risk. This scale explores ten other suicide risk factors, including sex (male), age, depression, history of suicide attempts, suicidal plans, excessive alcohol consumption, loss of rational thought, lack of social support, absence of spouse/partner and the presence of other pathologies. Adding smoking to this list would not complicate the administration, on the contrary: questioning about tobacco use seems easier than for other risk factors.

Smoking and mental health

Several theories attempt to explain the relationship between smoking and suicidal behavior. Some of them see a potential action of nicotine on the central nervous system leading to a decrease in MAO-A and B enzyme activity, which has already been identified as a source of greater impulsivity and loss of self-control, two established suicide risk factors. One of the authors, Gonzalo Haro, believes that these effects come from a decrease in serotonin, noradrenaline and dopamine that would be accentuated by smoking and would have an effect opposite to that of antidepressants[2]. Other hypotheses suggest a possible neurotoxic role of nicotine, which would promote anxiety and depression, or an effect of the decrease in oxygen in the blood (hypoxia).

Correlations between smoking and the presence of mental disorders have often been highlighted[3]. The exact causal relationship, however, remains to be established, even though it has been shown that tobacco consumption can contribute to the onset or worsening of depression, anxiety and stress. Quitting smoking not only promotes better overall health, but also has positive effects on mental health; it could be more integrated into the prevention and management of suicidal behaviour.

Keywords: Suicide, mental disorders, nicotine, risk factors, mental health

M.F.