Also reviewed on this blog was another film about mental illness shown on SNAM, "Shine" (1996).
“The Snake Pit” (1948) IMDb has Olivia de Havilland play the part of Virginia Cunningham, a young woman who finds herself locked up in a mental asylum. The film, taken from a novel by Mary Jane Ward and directed by Anotole Litvak, combines the point of view of the disoriented and harassed patient, Virginia, with external elements that keep the film firmly grounded in reality. In spite of the efforts of her loving husband (Mark Stevens) and Dr. Mark Kik (Leo Genn) to reach her, 
the harrowing experiences of the mental patient continue for a full two hours. “The Snake Pit” is an unusually honest film about mental illness for 1948 even if it does enter the realms of the melodramatic and over the top psycho-analysis at times.
Catch the TVO video trailer for "The Snake Pit" (1948)
See a segment of "The Snake Pit" (1948) with Olivia de Havilland.