Psychology was one of the first disciplines to study homosexuality as a discrete phenomenon. Prior to and throughout most of the 20th century, common standard psychology viewed homosexuality in terms of pathological models as a mental illness. That classification began to be tested in research, which hasn't produced strong empirical evidence regarding homosexuality as a disorder. A large number of professionals in medicine, mental health, and the behavioral and social sciences, "sit on the fence" regarding the classification of homosexuality as a mental disorder. In more recent years many have claimed the conclusion as accurate, and that the DSM classification reflected tested assumptions that were based on once-prevalent social norms and clinical impressions from "official" samples which