Introduction People with severe mental illness (SMI) have a higher risk of suicide compared with the general population. However, variations in suicide methods between people with different SMIs have not been examined. The aim of this pre-registered (PROSPERO CRD42022351748) systematic review was to pool the odds of people with SMI who die by suicide versus those with no SMI, stratified by suicide method.

Methods Searches were conducted on December 11, 2023 across PubMed, PsycInfo, CINAHL, and Embase. Eligible studies were those that reported suicide deaths stratified by SMI and suicide methods. Studies were pooled in a random-effects meta-analysis, and risk of bias was measured by the Joanna Briggs Institute checklist.

Results After screening, 12 studies were eligible (n = 380,523). Compared with those with no SMI, people with schizophrenia had 3.38× higher odds of jumping from heights (95% CI: 2.08–5.50), 1.93× higher odds of drowning (95% CI: 1.50–2.48). People with bipolar disorder also had 3.2× higher odds of jumping from heights (95% CI: 2.70–3.78). Finally, people with major depression had 3.11× higher odds of drug overdose (95% CI: 1.53–6.31), 2.11× higher odds of jumping from heights (95% CI: 1.93–2.31), and 2.33× lower odds of dying by firearms (OR = 0.43, 95% CI: 0.33–0.56). No studies were classified as high risk of bias, and no outcomes had high levels of imprecision or indirectness.

Conclusion These findings could inform lethal means counselling practices in this population. Additionally individual, clinical, community and public health interventions for people with SMI should prioritise, where feasible, means restriction including access to heights or drugs to overdose.