Freewheeling Cassavetes study of a marriage.
I think its a misreading to conclude that either one of the main characters is "crazy". Clearly Mabel has what you could call a borderline manic personality, but there's little evidence that she is unable to look after herself or her kids. The fact that she gets committed says less about her condition than about the position of women in the society Cassavetes is depicting. There is no sign that the visiting kids are in any danger - their father freaks out only because Mabel's behaviour falls outside his view of the conventional housewife. Nick on the other hand is not considered "crazy" despite physically attacking several people and getting his kids drunk, because men are allowed a lot more licence. In the end he is as trapped by the social pressures on him as Mabel is, except his frustration is turned outwards, hers inwards.
When the family are alone there is no problem, Nick's difficulties arise when Mabel is unable to fit the social role assigned to her - notably it is his mother who drives him to have Mabel committed. The "influence" Mabel is under turns out not to be alcohol as we first expect but patriarchy expressed via Nick, and society's limited and limiting expectations of women and of people in general. Put Mabel in a San Francisco commune 6 years earlier and she would look normal.
A word on the acting. Having known people with rather more serious cases of manic depression I can testify that Gena Rowlands' acting is actually rather understated. Falk meanwhile is a revelation to those who know him only from Colombo - his portrayal of the inarticulate, confused, occasionally violent but still very loving Nick is perfect - he just IS this guy.
Incidentally, you can see where Scorsese took many of the ideas for his most personal films from (notably "Mean Streets" which apparently he made after Cassavetes criticised "Boxcar Bertha") although he tidied them up and made them commercial. He even copied Cassevetes' lead here by putting his own mother in "Goodfellas".
