I have been told that A woman under the influence (1974 / Cassavetes) is a film that casts some light on many aspects of gendered oppression. After eventually having watched the film, I agree with this.
It is not, however, an easy film to watch. At many occasions, I felt like changing channels or pressing the stop-button. I tried to reflect on why I was overwhelmed by this reaction. Not only was it a very realistic movie, but the tension conveyed by the interaction between the actors was almost unbearable to endure. The atmosphere was intense in a way unlike anything else I have seen (Cassavetes' film is loud and quiet at the same time). All this is connected with what I saw as a very successful approach to storytelling; a lot of things were - in a way - kept open. Open not so that everything was reduced to guessing or hints, but open in the way that situations were often displayed in a complicated, rich manner.
As you probably know, the film focuses on a family, and especially on the relationship between the housewife-mother-wife and her blue-collar husband. By and by, we are made more familiar with how these two people perceive each other. This is, mainly, what the film is about. How we are perceived by others and what it means to be seen as a particular kind of person. Of course, in some way it deals with questions about mental illnesses - but it also relates these questions to gendered power. We get to see how the woman protagonist's reactions are constantly experienced by the other characters in the film as "embarrassing" or just an expression of mental deviance. I don't think that the movie actually would tempt one to ask whether she was really ill. What I rather tended to direct my attention at was the way the film described situations reaching a deadlock, in which everything turns from bad to worse (but I don't think that the film made any general claim about things being unchangeable).
Many aspects of the film reminded me of a film that is just as gruesome as A Woman Under the influence, namely: Alexandra's project (2003/ de Heer). These are both important films and I must say that I have learned a lot from both of them.