There are a number of newspaper articles mentioning the Hospital. In December 1924 it is noted as becoming a training school "for male and female mental nurses"
Saturday, Dec. 27, 1924
Publication: Nursing Times
Numerous advertisements for positions vacant etc up until February 1948 for "North Riding Mental Hospital, Clifton, York",
eg Wednesday, Feb. 18, 1948
Publication: Hull Daily Mail
then in February 1949 the ads are for "Clifton Hospital (Mental), York"
eg Tuesday, Feb. 22, 1949
Publication: Hull Daily Mail
I can also see a reference to J Ivison RUSSELL, "Medical Superintendent, the North Riding Mental Hospital" (being appointed to the Standing Mental Health Advisory Committee)
Saturday, Feb. 12, 1949
Publication: Nursing Times