It's really a roll of the dice. My mother was scared of me getting on Escitalopram because it gave her panic attacks but it was literally a silver bullet from me. 10mg a day turns me from a broken brain to a mostly normal human brain. It's such a lightswitch effect that sometimes I wonder if I'm overselling it to myself, and then I forget to get my prescription refilled for a couple days and I can feel that anxiety creeping back in from the edges, trying to make it's insidious way back into my life, and then I remember why I take it.
My understanding is that each SSRI type med has a roughly 30% chance of working for you, though the odds are slightly connected for SSRIs that are similar.
Completely anecdotally it seems to be much, much more effective for GAD than depression. I did have a panic attack on the 3rd or 4th day of taking it (and interestingly the only one I've ever had), but I kept going. 10mg to 20mg was the light-switch for me: I was on 10mg for about 3 months with no noticeable difference, and then 15mg (climbing to 20mg) was exceptional. I have a graph from the time when I was recording my mood 10-30 times a day, and it goes from being all over the place to just being in a relaxed state.
Also: "Escitalopram was well tolerated and only 7% patients withdrew, due to adverse events in the escitalopram group, versus 8% in the placebo group" -- people with anxiety disorders have panic attacks when they start lexapro at about the same rate as people who think they're on lexapro but aren't!
Also I do recommend trying any/all of the others things I mentioned as an adjunct, they've all got some decent science behind them, and defense in depth seems like a good idea to me.
My understanding is that each SSRI type med has a roughly 30% chance of working for you, though the odds are slightly connected for SSRIs that are similar.
If only the ADHD was as easy.