A different kind of gut–brain connection: Can lessons learned from reduction of colon cancer deaths guide enhanced suicide prevention?

In 1996, the American Cancer Society challenged researchers and clinicians to reduce mortality from cancer by half within 20 years. This was an ambitious aspirational goal and few at the time could have imagined just how achievable it ultimately proved to be. By 2015, colorectal cancer deaths, for instance, had been reduced by 47% in men and 44% in women, saving tens of thousands of lives each year in the United States alone (Byers et al., 2016). Crucially, this outcome arose from a multipronged effort that focused not just on identification of high-risk individuals and improved treatment for those with diagnosed colorectal cancer, but also on a comprehensive set of upstream interventions. These included (1) modifying distal risk factors, which for colon cancer meant efforts aimed at increasing dietary fiber and vegetables and reducing red meat, increasing rates of exercise and decreasing smoking; and (2) enhancing population-level endoscopic screening to facilitate early removal of potentially pre-cancerous adenomas. Notably, enhanced endoscopic screening informed by individual and age-related risk appears to have had the greatest impact, and this was enhanced by a massive media destigmatizing campaign encouraging people to get a colonoscopy.

In 2013, the World Health Organization issued a similar challenge asking countries to reduce suicide deaths by 10% by 2020. World rates of suicide per capita had diminished by 2% in 2016, the last year where data are available (Lee et al., 2019), but clearly much more work is still needed. This begs the question, can efforts at reducing colon cancer deaths be a model for suicide prevention? Just as there are many types of cancer, numerous mental disorders confer risk of suicide. Here, we will explore implications for bipolar disorder (BD), a disorder that confers one of the highest suicide risks, as an example that could be applied across psychiatric disorders.

Consider Patient A—an outpatient with BD type I being seen regularly by their psychiatrist and also having periodic contact with their primary care provider. Patient A has not been hospitalized for many years, but has dealt with intermittent periods of depression and anxiety. Then, let us consider Patient B—who also has BD type I and was recently seen in the emergency department (ED) for severe depression with anxiety but has no established psychiatric follow-up. All would agree that at an individual level, Patient B is at greater short-term risk of suicide. Yet, what about at a population level? Are more people like Patient A going to die from suicide than people like Patient B? Or vice versa?

Data from our research group recently examined health care contacts prior to suicide death among 176 suicide decedents with BD. We found that while only 38% had an ED visit (mean = 2.5 visits) during the year prior to death, 76% had an outpatient psychiatric visit (mean = 17.2 visits) and 75% had a mental health-related primary care visit (mean = 7.0 visits) (Schaffer et al., 2017).

Other groups have also shown that most suicides in people with BD occur during periods of pure depression, not because this is the highest risk period (which is notably during episodes with mixed features) but because more time is spent in depression by a greater number of patients with BD (Persons et al., 2017). These results together reflect the likelihood that there are many more ‘Patient A’ than ‘Patient B’ deaths due to suicide, simply because there are many more Patient As, even if each individual patient may be at lower risk.

The implications for suicide prevention are clear. Just as in the effective program for reducing colon cancer mortality, a focus solely on aggressive interventions in the highest risk groups is unlikely to be sufficient. All people with BD are at elevated risk of suicide, and most deaths may be occurring in patients not necessarily deemed to be at highest risk. Suicide prevention strategies such as ensuring continuous effective mood stabilization, developing written safety and healthy coping plans, ensuring access to care during high-risk periods and common sense means restriction during periods of distress (e.g. removal of firearms or easy access to large quantities of medications) must therefore be considered for all patients with the condition, not just those who are deemed to be past an artificial ‘high risk’ line. Moreover, research suggests that even modest reductions in population-based risk factors for suicide such as socio-economic deprivation across entire societies can potentially have a much larger positive impact on suicide rates than moderate size reductions in known risk factors that are less prevalent (e.g. better treatments for specific mood disorders; Li et al., 2011).

No one strategy is sufficient, and suicide prevention efforts should take a lesson from the success seen in preventing deaths from colon cancer. To reach our goals, suicide prevention must take a view toward interventions across much larger clinical populations and the population at large.