Amphetamine was discovered as a drug in the late 1920s, and its pharmacological effects on attention and cognition, emotions, and appetite were explored thoroughly in the 1930s and 1940s. By the late 1940s, it had achieved medical and market success as an antidepressant and was quickly gaining such success as a diet medication. In contrast, both careful testing and extensive military experience had left the impression that the drugs’ benefits for attention and cognition were more subjective than real and that any objective benefits were explained mainly by the drug's mood-elevating effects. Because of its unpatentable status, methamphetamine had been introduced for all the same uses by drug firms competing with the holder of the amphetamine patent. The drugs were being widely used nonmedically and their abuse potential was becoming recognized by medicine, eventually leading to their strict control internationally around 1970.