Means restriction for the prevention of suicide by jumping

Jumping from a height is an uncommon but lethal means of suicide. Restricting access to means is an important universal or population-based approach to suicide prevention with clear evidence of its effectiveness. However, the evidence with respect to means restriction for the prevention of suicide by jumping is not well established.

To evaluate the effectiveness of interventions to restrict the availability of, or access to, means of suicide by jumping. These include the use of physical barriers, fencing or safety nets at frequently-used jumping sites, or restriction of access to these sites, such as by way of road closures.

We searched the Cochrane Library, Embase, MEDLINE, PsycINFO, and Web of Science to May 2019. We conducted additional searches of the international trial registries including the World Health Organization International Clinical Trials Registry Platform (ICTRP) and ClinicalTrials.gov, to identify relevant unpublished and ongoing studies. We searched the reference lists of all included studies and relevant systematic reviews to identify additional studies and contacted authors and subject experts for information on unpublished or ongoing studies. We applied no restrictions on date, language or publication status to the searches. Two review authors independently assessed all citations from the searches and identified relevant titles and abstracts. Our main outcomes of interest were suicide, attempted suicide or self-harm, and cost-effectiveness of interventions.

Eligible studies were randomised or quasi-randomised controlled trials, controlled intervention studies without randomisation, before-and-after studies, or studies using interrupted time series designs, which evaluated interventions to restrict the availability of, or access to, means of suicide by jumping.

Two review authors independently selected studies for inclusion and three review authors extracted study data. We pooled studies that evaluated similar interventions and outcomes using a random-effects meta-analysis, and we synthesised data from other studies in a narrative summary. We summarised the quality of the evidence included in this review using the GRADE approach.

We included 14 studies in this review. Thirteen were before-and-after studies and one was a cost-effectiveness analysis. Three studies each took place in Switzerland and the USA, while two studies each were from the UK, Canada, New Zealand, and Australia respectively. The majority of studies (10/14) assessed jumping means restriction interventions delivered in isolation, half of which were at bridges. Due to the observational nature of included studies, none compared comparator interventions or control conditions. During the pre- and postintervention period among the 13 before-and-after studies, a total of 742.3 suicides (5.5 suicides per year) occurred during the pre-intervention period (134.5 study years), while 70.6 suicides (0.8 suicides per year) occurred during the postintervention period (92.4 study years) - a 91% reduction in suicides. A meta-analysis of all studies assessing jumping means restriction interventions (delivered in isolation or in combination with other interventions) showed a directionality of effect in favour of the interventions, as evidenced by a reduction in the number of suicides at intervention sites (12 studies; incidence rate ratio (IRR) = 0.09, 95% confidence interval (CI) 0.03 to 0.27; P < 0.001; I² = 88.40%). Similar findings were demonstrated for studies assessing jumping means restriction interventions delivered in isolation (9 studies; IRR = 0.05, 95% CI 0.01 to 0.16; P < 0.001; I² = 73.67%), studies assessing jumping means restriction interventions delivered in combination with other interventions (3 studies; IRR = 0.54, 95% CI 0.31 to 0.93; P = 0.03; I² = 40.8%), studies assessing the effectiveness of physical barriers (7 studies; IRR = 0.07, 95% CI 0.02 to 0.24; P < 0.001; I² = 84.07%), and studies assessing the effectiveness of safety nets (2 studies; IRR = 0.09, 95% CI 0.01 to 1.30; P = 0.07; I² = 29.3%). Data on suicide attempts were limited and none of the studies used self-harm as an outcome. There was considerable heterogeneity between studies for the primary outcome (suicide) in the majority of the analyses except those relating to jumping means restriction delivered in combination with other interventions, and safety nets. Nevertheless, every study included in the forest plots showed the same directional effects in favour of jumping means restriction. Due to methodological limitations of the included studies, we rated the quality of the evidence from these studies as low. A cost-effectiveness analysis suggested that the construction of a physical barrier on a bridge would be a highly cost-effective project in the long term as a result of overall reduced suicide mortality.

The findings from this review suggest that jumping means restriction interventions are capable of reducing the frequency of suicides by jumping. However, due to methodological limitations of included studies, this finding is based on low-quality evidence. Therefore, further well-designed high-quality studies are required to further evaluate the effectiveness of these interventions, as well as other measures at jumping sites. In addition, further research is required to investigate the potential for suicide method substitution and displacement effects in populations exposed to interventions to prevent suicide by jumping.