Suicide prevention through means restriction: impact of the 2008-2011 pesticide restrictions on suicide in Sri Lanka

Objective: To investigate the effect of 3-year phased bans of the pesticides dimethoate and fenthion in 2008-2010, and paraquat in 2009-2011, on suicide mortality in Sri Lanka.

Methods: Age standardised overall, sex specific, and method-specific suicide rates were calculated using Sri Lankan police data (1989-2015). Using negative binomial regression models, we estimated the change in the rate and number of suicide deaths in post-ban years (2011-15) compared to those expected based on pre-ban trends (2001-10).

Findings: Overall suicide mortality dropped by 21% between 2011 and 2015, from 18.3 to 14 per 100,000. The decline in pesticide suicides during this same period was larger than for overall suicides: from 8.5 to 4.2 per 100,000, a 50% reducition. This was accompanied by a smaller concurrent rise in non-pesticide suicide mortality with a 2% increase (9.9 to 10.1 per 100,000). In 2015, the raio between the observed and expected pesticide suicide rates was 0.49 (95% confidence interval [CI] 0.40, 0.62), corresponding to an estimated 937 (95% CI 574, 1389) fewer pesticide suicides than expected from pre-ban suicide rates. Findings were similar in sensitivity analyses using 2008 or 2012 as commencement of the post intervention period.

Conclusion: Bans of paraquat, dimethoate and fenthion in Sri Lanka were associated with a reduction in pesticide suicide mortality and in overall suicide mortality despire a small rise in other methods. This study provides further evidence for the effectiveness of pesticide regulation in limiting the availability of highly hazardous pesticides and thereby reducing the number of global suicides.