Hi! I have a lot to say on this topic! I'm actually going to copy and paste a post I made in 2023, then I'll follow it with an update:

"Hi! You are absolutely right, side effects ARE different for everyone! I can tell you my personal experience with all three AIs and Tamoxifen. It's a long story! I began with Anastrozole. It was wonderful for the first two months; I remember thinking that I was so lucky to have zero side effects, it was like I wasn't even on meds. But about two months in, my thumbs began locking and it got worse quickly. When it got to the point that to unlock them from a bent position, I had to manually pop them straight (kinda painful, not hideously), my doc and I decided to try a different AI. After a short break (1-2 weeks) during which my trigger thumb rapidly improved, I began Letrozole, and the trigger thumb returned almost immediately. I will note here that on both of these AIs, after about two months I did experience mild joint pain. It was mostly in the morning (I'd creak and hobble around for a little bit and then be fine), nothing debilitating, and were it not for the trigger thumb, I would have happily endured it. At this point, though, I was worried that the trigger thumb would eventually require surgery to remedy, so we switched to Tamoxifen. Another quick note, the trigger thumb/finger is a very rare side effect of AIs; my onc had never actually seen a patient with this, although she was aware of the possibility. So, now on Tamoxifen, I again had zero side effects, thinking hooray, but at that two-month mark, I was walloped by intense anxiety, quickly followed by deep depression. I have thankfully never had to deal with anxiety/depression before. This was the absolute worst experience of my life; I cannot communicate how terribly it affected me. I couldn't sleep, I couldn't eat, I (a wife and mother of two kids, 9 and 12) temporarily stayed with my mom and she took constant care of me. We went to every doctor we could think of trying to get to the bottom of this. A psychiatrist prescribed Pristiq, I had many sessions with a therapist, I had all my bloodwork checked, I visited my OB/Gyn, I saw my breast surgeon, all to no avail. I had no earthly clue where the anxiety/depression came from, but for two months I was in hell. I begged for a drug to just knock me out til this was over. I was so close to voluntarily admitting myself to the psych ward. My brother researched the heck out of my situation, and found a ton of anecdotal evidence online that for many women, Tamoxifen can cause severe anxiety and depression. Really?! My oncologist said there was no known reason for that, it's not listed as a possible side effect at all, the entire medical community seems to deny any link. But she agreed to let me go off the Tamoxifen to see if it helped. And in a matter of days, I was better. In 1-2 weeks I was entirely back to my old self, looking back and wondering what in the world had just happened. My onc was glad I was back to myself, but still doesn't acknowledge a link between Tamoxifen and anxiety/depression. After a month I started Exemestane, the last AI left to try. It's been four months, and I am great, no side effects! No trigger thumb, no joint pain, nothing. Now, a few things to note: this entire time, because I am premenopausal, I have been receiving Zoladex injections to suppress my ovaries. I am certain it has not affected anything at all and I have never experienced any side effects from it. (I began the Zoladex prior to taking the first AI). Second, I am still taking Pristiq (an antidepressant). I really don't believe it helped the anxiety/depression, because I was taking it long before quitting Tamoxifen, and I saw no improvement at all until I quit the Tamoxifen. However, my brother did uncover in his research (thanks, Matt!) that the Pristiq may help with joint pain! Is it helping prevent trigger thumb? I see the psychiatrist tomorrow, and we plan to wean me off the Pristiq, so I will find out! My psych (and the web) agrees that some antidepressants can help relieve chronic pain, which is interesting in itself.

This is all in no way to say that Tamoxifen will cause anxiety/depression, just that it can. I know many women who did not experience this on Tamoxifen, and I know one who went through the exact same hell I did (I am 47, she is 31. The women I know who did not have anxiety/depression on Tamoxifen were all 60+, not sure if it's relevant). I passionately wish the medical community would study this further. If anxiety/depression were listed as a possible side effect of Tamoxifen, it would have saved me untold time, energy, money, and most importantly, misery. Even though trigger finger is an extremely rare side effect of AIs, because it IS acknowledged, my doc and I knew exactly where to look first for the cause. If it was not listed/acknowleged, I would have probably have gone crazy trying to figure out what was happening. And that is exactly what happened with the anxiety/depression. My family and I went around in circles, desperately trying to find the cause so we could fix it. I'm honestly furious about the whole situation, although at the same endlessly relieved and thankful to be on the other side of that dark, dark time.

Whew, sorry to write a book here, but I just want to share my experience in case it can help even one person! Anyone is welcome to contact me about this topic, or indeed, about anything if you think I can help in any way. Hugs to every single one of you out there."

Update: I'm still on Exemestane and doing good! I will say I feel about a hundred years old sometimes (I'm 50 now). I get stiff from sitting too long, sore from standing or walking too long, and I've developed hip pain (possibly impingement). How much of this is from the AI and how much is normal aging, I don't know. But most importantly to me, I have had NO depression or anxiety since quitting Tamoxifen. And I did quit the Pristiq shortly after writing that post. There is no doubt in my mind that Tamoxifen caused all the trouble I described above. Your actual question was about AIs and depression! In my experience with all three, none of them caused me any kind of depression or anxiety. But like I said, an AI that's great for one woman might not be for another, and vice versa. I think most docs are pretty open about switching AIs if one gives you trouble. Good luck!