ImportanceRates of grief-related psychiatric conditions, such as prolonged grief disorder (PGD), posttraumatic stress disorder (PTSD), and major depressive disorder (MDD), among bereaved adults in the US are largely unknown due to limited studies that leverage national samples.ObjectiveTo assess risk factors for and prevalence rates and co-occurrence of PGD, PTSD, and MDD among bereaved adults in the US.Design, Setting, and ParticipantsData for this survey study were collected from a large US panel sample between October 10 and 28, 2022, using a web-based survey. Participants were aged 18 years or older and were proficient in English. Data analysis was conducted between March and June 2023.Main Outcomes and MeasuresProbable psychiatric conditions were assessed with validated measures that used conservative cutoff scores, duration, and impairment criteria. These measures included the revised Prolonged Grief Disorder scale for PGD, the PTSD Checklist for DSM-5 for PTSD, and the Patient Health Questionnaire-9 for MDD. Data were analyzed using basic descriptives and logistic regression.ResultsA total of 2034 adults (n = 1529 and 505 in the bereaved and comparison groups, respectively) completed the study. Respondents had a mean (SD) age of 40.7 (15.9) years; the majority were women (1314 [64.6%]) and had at least some college experience (1394 [68.5%]). With regard to race and ethnicity, 392 respondents (19.3%) were Black, 138 (6.8%) were Hispanic, and 1357 (66.7%) were White. Among bereaved adults, 312 (20.4%), 518 (33.9%), and 461 (30.2%) met criteria for a presumptive diagnosis of PGD, PTSD, and MDD, respectively. Comorbidities were common, with 441 participants (28.8%) meeting criteria for at least 2 co-occurring disorders. Comorbid PGD, PTSD, and MDD were more common than any 2 co-occurring or isolated disorders; the presence of co-occurring conditions was more likely among respondents who reported a traumatic loss. Age and educational attainment were associated with the risk of psychiatric conditions; less time since the index death, loss of a psychologically close other, and a traumatic loss experience were associated with increased risk of PGD, PTSD, and MDD or their co-occurrence.Conclusions and RelevanceIn this study, the majority of bereaved adults did not meet presumptive criteria for PGD, PTSD, or MDD. Nevertheless, PGD, PTSD, and MDD were highly prevalent and comorbid, particularly among those who experienced traumatic loss. These findings underscore the need for integrated psychological care that leverages transdiagnostic mechanisms of evidence-based practice.