The problems that affected Judy Garland and contributed to her early death are well known, and we don't wish to go through them again in detail here. Sadly, it's highly likely that they started on the set of 'The Wizard of Oz', where as an impressionable young girl she was fed drugs by people who should have had a duty of care over her.
It was important to the studio making the film that Garland should retain her appearance both during the filming of the movie, and all promotional appearances on its release. This meant keeping her young looking, and skinny. The problem was that Garland was at an age where she was naturally becoming more womanly, at a rapid pace. To counter this, she was given nicotine, amphetamines and other drugs to keep her weight down. This would be unthinkable in the modern age, and result in the immediate arrest of everybody involved, but was common practice in the 1930s.