This is an excellent question and one that goes to my thoughts about the writing style of this author which I discussed in earlier questions. I don't really know if Emma's loss is connected to what Leo tells us seems to be a sort of hoarding of things on Emma's part. I certainly see and understand a connection between the two. She has lost a son and having kept that secret from the man she lives with, she is filling their home up with "stuff" just as she keeps her secret past stuffed inside herself. However, it seems that this might be one of those aspects of the novel that is not well developed - hoarding may symbolize her loss but the author does not develop this idea well enough or finitely enough for us to know for certain. This is a good example of what I refer to when I say writing style is the weakness in this novel - not plot line. In future works I'm sure Walsh will learn to develop these peripheral ideas further.
With regard to whether the statement is true or not in general, I'm truly not sure. My best guess would be more no than yes. When an individual feels his or her life is falling apart, is bereft of hope, often it seems that is when mental health begins to break down - as it did for Janice. She was at the end of her rope so to speak. Emily was not at that point - she used hoarding to deflect reality, to keep from telling the truth. Janice could no longer manage to hold her world together - and we saw it fall completely apart.