Generalized anxiety disorder (GAD) is a major public health concern. It is frequently under-recognized or misdiagnosed, especially in the elderly. It is associated with high comorbidity and disability, and a low rate of full remission. Despite substantial socioeconomic and public health consequences, there has been little research to identify GAD determinants in general elderly populations. The aim of this thesis was to provide a deeper understanding of the clinical characteristics and risk factors for GAD in late life from the prospective ESPRIT study of 2259 community-dwelling French elderly (aged 65 years and over) examined six times over 12 years.The 6-month current prevalence of GAD was 4.6%, 14% of the cases were comorbid with major depression and 35% with phobia but the factors associated with these disorders differed. During the 12-year follow-up, 8.4% of the participants experienced incident GAD (10 per 1000 person-years) of which 80% were first episodes. Multivariate statistical models showed that the main predictors for late-life GAD were being female, reporting recent and childhood adverse life events, having chronic physical (respiratory disorders, arrhythmia and heart failure, cognitive impairment, dyslipidemia, and adiposity), and mental (major depression, phobia, and past GAD) disorders. Specific genetic variants of adrenergic receptors increase the risk of GAD (but not phobia) and moderate the effect of adverse life events. GAD can be characterized as a multifactorial stress-related affective disorder resulting from both proximal and distal risk factors, and is clinically distinct from other major psychiatric disorders in the elderly.This work provides new knowledge on GAD determinants with clinical implications for diagnosis and etiology. It could also contribute to developing novel preventative and intervention strategies in the elderly, with major potential consequences for overall health and daily functioning.