Suicide is a tricky public health issue, with experts and policymakers attempting to address both the roots of the problem and the crucial moments of crisis when people try to act on their suicidal feelings. Yet it’s still the second leading cause of death among those 25 to 34, and the third among those ages 15 to 24. Worldwide, there are more than 800,000 suicides every year. It’s still nearly impossible to identify those at risk for suicide before they begin exhibiting suicidal thoughts or behaviors in the first place. But a new international review has taken a look at all the methods available to reduce suicides and determined that some really do work while others show little effectiveness.

Researchers from the European College of Neuropsychopharmacology and the Expert Platform on Mental Health, Focus on Depression examined almost 1,800 studies on suicide published over ten years. The authors’ results were printed in Lancet Psychiatry.

One important finding was that restricting a person’s access to ways of committing suicide has a significant impact. Erecting barriers at popular suicide spots like high bridges and restricting the number of pills in packets are two measures that have proven effective. Places that have stricter gun licensing laws also have lower suicide rates. The report notes that if impulsive attempts at suicide could be blocked, many lives could be saved.

Addressing depression, which is an important risk factor for suicidal behavior, also proved to be effective in certain populations. Medicines like lithium and clozapine have reduced suicides among those over 75, but in children and adolescents the drugs may actually increase suicidal thoughts. Untreated depression, however, is also a risk, so the problem is highly personal and consequently complicated.

Additional methods that showed some positive effects included placing professionals trained to recognize at-risk behavior in schools, but this was only useful if integrated with other suicide prevention measures. The study also noted that following up with those who have previously attempted suicide is strongly recommended.

“We found that there is no single way of preventing suicide,” Zohar said in a press release. “However, implementation of the evidence-supported methods described in this study, including public and physician education and awareness together with appropriate legislation, has the potential to change public health strategies in suicide prevention plans. With these measures, we can significantly reduce the number of deaths due to suicide.”

The president of the European College of Neuropsychopharmacology, psychiatry professor Guy Goodwin, said the college was proud to have supported such a definitive review.

“As is still not sufficiently known, suicide is always among the commonest causes of death in young people,” he said. “Policies to reduce it need to be evidence-based and this review highlights where evidence does and does not exist currently.”

Source: Zalsman G, Hawton K, Wasserman D, van Heeringen K, Arnsman E, Sarchiapone M, et al. Suicide Prevention Starategies Revisited: 10-year Systematic Review. Lancet Psychiatry. 2016.