I suppose it also depends on the individual person's attitude. I mean, discussion of politics and political issues can be an interesting and entertaining "brain exercise" without necessarily leading to stress... whereas some people might find that kind of thing more stressful.

Similarly, I find discussion about people and/or relationships to be quite "intellectual" in nature because such topics deal with psychology, even if the people holding the conversation don't realise that's what they're engaged in and don't use "intellectual" terminology. And pretty well everyone on earth talks about other people! It's surprising how much really complicated interaction and stuff goes on within a conversation that sounds shallow and rather ordinary on the surface.