I honestly don't think it's hypoglycemia, though.
Diabetes is in his family, so there's actually a good chance of it being hypoglycemia. It's usually the first step for full-blown diabetics. A lot of people think that they have depression but what they really need to do is control their blood sugar. For every glucose-high, there is an equal and opposite low.
Can I do something about this, something diet-related?