Hi
I would personally be inclined not to rule out your TKI causing or at least contributing to your symptoms. I believe if you Google low mood or depression and Nilotinib (Tasigna) in the side effect profile this is indeed listed.
My response is from a personal point of view, and maybe from someone who is in the unique group of being on all four TKIs over the past 2 years - with problems. I can say that my mood on Dasatinib was so noticeably low that my wife even noticed a massive change in me, on switching to Bosutinib, my pain and other issues remained but my mood is completely different and back to how I have always been. Nilotinib didn't change my mood at all, but that is me, and I am different to you, as you are different to others on here.
I again, from a personal point of view think it would be foolish to automatically assume it is just the TKI, but it would be equally foolish to rule it out. If caffeine can affect some, but not others, some kinds of alcohol, drugs and even food groups, it would be silly to believe a certain TKI would be immune to chemical changes affecting your mood. These drugs are potent, they have to be, if they can give some bone pain, some gastro issues, some dermatological changes, why not issues causing your mood to suffer?
I would at least chat to your consultant and nurse to see if they have experienced this.
As it has been said, Cancer is still a big diagnosis and it will impact on you at certain spells, it has to. Remember this forum is here for you to speak to fellow CML'ers.
Take care and be kind to yourself.
John