Harvard scientists link coffee drinking to 45% lower suicide risk


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Picture Credit: James Joel/Flickr
Picture Credit: James Joel/Flickr

Related tags Caffeine

Harvard scientists say their new study supports an association between drinking two to three cups of coffee daily and a 45% lower risk of suicide.

But asked if caffeine could be used to treat depression in a clinical context, co-author Professor Alberto Ascherio, professor of epidemiology and nutrition, Harvard School of Public Health, told“I doubt that caffeine can be used…unless the depression itself is due to caffeine withdrawal in a previously habitual drinker. I.e. sudden suspension of caffeine could precipitate depression in some individuals, and caffeine could fix this.”

The study by eminent academics, Michel Lucas is the lead author, explains that caffeine may act as a mild anti-depressant by boosting production of certain neurotransmitters in the brain, including serotonin, dopamine and noradrenaline.

But the scientists, writing in The World Journal of Biological Psychiatry​, do not recommend depressed adults increase their caffeine consumption, as any increases could lead to side-effects.

“Overall, our results suggest that there is little further benefit for consumption above two to three cups or 400mg of caffeine per day,”​ Lucas et al. write.

Large-scale public health surveys

The scientists set out to evaluate the association between coffee and caffeine consumption and suicide risk in three large-scale public health surveys of US men and women.

The team assessed Harvard data of 43,599 men enrolled in the Health Professionals Follow-Up Study, 73,820 women in the Nurses’ Health Study (NHS) and 91,005 women in the NHS II study.

Consumption of caffeinated and decaffeinated coffee was assessed every four years – the datasets taken together cover 1988 to 2008 – using food-frequency questionnaires – and Lucas et al. took into account potential confounders such as marital status, smoking, alcohol intake, BMI, exercise.

Suicide deaths were determined by physician review or death certificates, and the team documented 277 deaths via this means.

Compared to those drinking around one cup of caffeinated coffee a week greater than 8oz (237ml), the pooled multivariate relative risk (RR) of suicide was 0.55 (0-38-0.78) or 45% lower for those consuming two to three cups daily.

Risk of chance association?

But critiquing the study, the UK National Health Service (NHS) noted that suicide was rare in the groups studied (0.1%) and said that “any study relying on small numbers has a high possibility that any associations found will be due to chance”.

Unmeasured confounding factors could also have affected the results, the NHS said. For instance – one example cited by the study authors themselves – the possibility that people who feel anxious may avoid drinking coffee as it worsens their symptoms.

Prof. Ascherio told us it was difficult to determine whether the association was causal or not. “I believe that the overall evidence favors a causal interpretation, but does not prove it,”​ he said.

“It remains possible that those individuals who do not tolerate caffeine are more prone to depression and suicide.”

Title:​ ‘Coffee, Caffeine and Risk of Completed Suicide: Results from Three prospective Cohorts of American Adults’

Authors:​ Lucas, M., O’Reilly, E.J., Pan, A. Mirzaei, F., Willet, W., Okereke, O.I, Ascherio, A.

Source:The World Journal of Biological Psychiatry​, Published online July 2 2013, doi:10.3109/15622975.2013.795243

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