This article proposes a revision of the historical evolution of the concepts of generalized anxiety disorder (GAD). Currently, Darwin's evolutionary theory is the hegemonic paradigm for modern science and influences research on mental disorders. Throughout the 20th Century, the editions of the Diagnostic and Statistical Manual of Mental Disorders (DSM; American Psychiatric Association) have changed the diagnostic criteria for GAD, reflecting the prevailing psychiatric understanding of this disorder. The prevalence and symptoms of major depression and GAD show the fragility of the categorical conception of these conditions. Differences in cultural views towards anxiety disorders also suggest that anxiety cannot have a uniform definition. This article provides contributions for reflecting future guidelines concerning the diagnostic criteria for GAD in DSM-V.