I think everyone, whether on meds or not, tends to drift off when someone is talking about a subject they're not interested in, especially when it's something they constantly yammer about. I try to be an 'active' listener, but sometimes my husband gets on these tangents about things he invents in his head but never takes any action on, and he rambles about specifications and applications of these inventions.... and I'm off in la-la land, chiming in w/the obligatory 'Yes dear', 'That's a good idea, dear'... Of course, sometimes he catches onto the fact that I am not paying him any attention & will say something off-the-wall like, "So, are we going to have **** sex tonight?" to which I automatically reply, "Yes, dear".

Now, as far as your husband actually calling you 'dumb' - I'd kick his ***. It is hurtful, disrespectful and just mean. Instead of letting him ramble on, let him know that you aren't interested in the stock market or global economics - and if you want conversation, find a topic you can focus on or let him know that you aren't in a frame of mind for talking.