I have a completely home grown unproven theory (given I am an engineer, not a doctor) that depression in some manifests with overpowering feelings of introspection ... as things relate to that person ... and that is a viscious spiralling thing ... to the person, the world is spinning in towards them ... it would feel frightful.
That being the case, I wonder if strategies that include volunteering, giving, helping ... energy flowing outward from the person to others ... might be helpful?
Mrs Dex is a GP and she would definitely say your son in law needs the right help ... and you likewise for the support it would give you.
