Background <p>There is a paucity of research that has examined how significant health, social, and environmental crises impact suicidal ideation, particularly where these events co-occur and have potentially synergistic adverse effects. The aim of this study was to identify the unique and cumulative contributions of mental health, social, and environmental risks on 12-month trajectories of suicidal ideation.</p> Methods <p>A community-based sample of 1928 Australians (aged ≥ 16 years) completed online surveys measuring mental health, social, and environmental risk factors, and suicidal ideation at baseline, and the suicidal ideation measure was repeated at four follow-up timepoints. Growth mixture modelling identified suicidal ideation trajectories and multinomial logistic regression analyses examined associations between baseline risk variables and the trajectories.</p> Results <p>Analyses showed five different trajectories of suicidal ideation (one stable low ideation trajectory; four vulnerable trajectories). A different set of risk factor variables predicted each vulnerable trajectory relative to the low trajectory. A cumulative risk index representing the combined effects of the mental health, social, and environmental risk factors also predicted each vulnerable trajectory relative to the low trajectory.</p> Conclusions <p>While adversity resulting from exposure to health and environmental crises was associated with suicidal ideation, the heterogeneity in how patterns of mental health, social, and environmental factors related to trajectory classes suggests that people experience these events differently. A cumulative risk index may be a potentially useful indicator of risk.</p>