Final answer:
David Rosenhan's study exposed the questionable reliability of psychiatric diagnoses and the need for reforms in mental health systems. It showed how labels of mental illness could result in dehumanizing treatment and influenced the push for patient rights and deinstitutionalization in the 1960s and after.
Step-by-step explanation:
David Rosenhan's study in mental hospitals primarily shed light on the issue of the validity of psychiatric diagnoses and the effects of institutionalization on individuals. His seminal work, often referred to as the Rosenhan experiment or 'On Being Sane in Insane Places,' raised significant questions about the reliability of psychiatry as a science and sparked discussion about the reforms in the mental health systems. Published in the science journal Science in 1973, the study revealed how healthy individuals, who briefly reported auditory hallucinations, were admitted to psychiatric hospitals and subsequently struggled to be discharged despite behaving normally thereafter.
This groundbreaking research illustrated how labels of mental illness could lead to dehumanizing treatment and supported the movements for social change and liberation within psychological practice. It aligned with a broader critique of psychiatric practices by other scholars of the era such as Erving Goffman's work Asylums and contributed to the push towards deinstitutionalization and improved patient rights during the 1960s and beyond.