Objective-Recent studies have found that a subset of young adult survivors of childhood cancer report posttraumatic stress symptoms in response to their diagnosis and treatment. However, it is unclear if these symptoms are associated with impairment in daily functions and/or significant distress, thereby resulting in a clinical disorder. Furthermore, it is unknown whether this disorder continues into very long-term survivorship, including the 3 rd and 4 th decades of life. This study hypothesized that very long-term survivors of childhood cancer would be more likely to report symptoms of posttraumatic stress disorder, with functional impairment and/or clinical distress, compared to a group of healthy siblings.Patients and Methods-6,542 childhood cancer survivors over the age of 18 who were diagnosed between 1970 and 1986 and 368 siblings of cancer survivors completed a comprehensive demographic and health survey.Results-589 survivors (9%) and 8 siblings (2%) reported functional impairment and/or clinical distress in addition to the set of symptoms consistent with a full diagnosis of Posttraumatic Stress Disorder (PTSD). Survivors had more than a four-fold risk of PTSD compared to siblings (OR=4.14, 95%CI: 2.08-8.25). Controlling for demographic and treatment variables, increased risk of PTSD was associated with educational level of high school or less (OR=1.51, 95% CI=1.16-1.98), being unmarried (OR=1.99, 95% CI=1.58-2.50), annual income less than $20,000Address correspondence to Margaret L. Stuber at UCLA Semel Institute, 760 Westwood Plaza, Los Angeles, CA 90024-1759. Telephone: 310 825-5213, Fax: 310 206-4446, mstuber@mednet.ucla (4), one symptom of re-experiencing, three avoidance symptoms, and two symptoms of increased arousal must be present. In addition, symptoms must be severe enough to cause clinical distress or functional impairment. Symptoms must also be in response to an event that ended at least one month prior to assessment, was perceived as a threat to life or body integrity of self or a loved one, and elicited feelings of horror, intense fear or helplessness.Previous studies of PTSD in childhood cancer survivors have found a minority of survivors reporting significant symptoms, with as few as 3% of survivors 8 to 20 years old (1) to 20% in young adult survivors (2). Compared to a rate of 8.6% in a recent study of 965 adults attending a primary care clinic (5), young adult survivors, but not younger survivors, appeared to have a significantly increased prevalence of PTSD symptoms. Although no formal assessment of clinical distress or functional impairment was done as a part of the diagnosis, the young adult survivors who reported symptoms of PTSD were less likely to be married, and reported more psychological distress and poorer quality of life across all domains (6). Similar impairments in function have also been described in people with PTSD within the general population (5, 7).Subsequent studies of PTSD in adult survivors of childhood cancer with sample sizes ranging from 45 to 368 ha...