We have previously shown (Gratch et al., 2021) that in depressed individuals, Ecological Momentary Assessment (EMA) captures instances of suicidal thinking that go undetected through retrospective report. From the same study, we now report on SI in healthy volunteers (HVs, n=42) and patients with Major Depressive Disorder (MDD, n=80) using EMA, and compare their SI characteristics and the impact of life events on SI. Both groups provided 7 days of Ecological Momentary Assessment (EMA) data about SI, measured by 9 Likert scale items, and life events. Repeated-measures Wilcoxon rank test for clustered data, longitudinal mixed effects regression and mixed effect logistic regression models compared HV and patient reports of SI and life events, and tested differences in HVs’ and patients’ SI score change from the previous epoch’s SI score when each of the life events occurred relative to no event. We found that HVs reported positive SI score in 44% of EMA epochs, including 11% of epochs with at least one of the following items endorsed: “thoughts about dying,” “a wish to die,” “a wish to sleep and not wake up,” “suicidal thoughts as a wish to escape,” “thoughts about hurting yourself,” “an urge to hurt yourself,” and “thoughts of killing yourself”. As expected, HVs reported less frequent (p<0.001) and less intense SI (p<0.003) than patients. Both patients with MDD and HVs most often manifested passive SI (“a wish to live [reverse coded],” “reasons for living [reverse coded]”). For 7 of 8 types of stressors, patients with MDD reported more stressors than HVs (all p<0.001), responding to them with increased SI (0.0001