This is a very well-considered question, very insightful. It's a hard thing to say, but many Irish struggle with depression. Part of the blame can be laid on the weather, which is often wet, cold, and dreary, and sucks the life out of people. I've often seen it in action. The winter is a depressant. The summer, with its long days, is an anti-depressant. Also, one would be remiss if there was no mention made of alcoholism and in recent generations, add drug use to that.
Eye contact is generally direct in the Irish people. They will look you straight in the eye, which is an indication of the general hospitality attributed to the race. When you see an Irish person who will not do so, look a little deeper. There is a good chance he or she is not well. Personal space is important, though privacy is often difficult to achieve in small houses with large families. A modesty screen is very much appreciated by people who often dress and undress with their backs to you in a closet. I am being very frank now. Of course this is not the case in every family, but it is especially prevalent among people who are not very well off. I cannot address religion as it impacts these things as each person only knows their own.
Best wishes,
Mary Ellen