I've only been taking synthroid for a little over 2 months and not only has my husband noticed behavioral changes with me but I feel them as well. If I didn't know what depression felt like, I would say that would be the problem, however; it's a lot more than that. I've felt "sad", as though my heart were breaking and then I get angry and have the "I don't care" attitude. Mood swings galore which is very unlike me. I'm naturally a very outgoing and friendly person who has turned to the irate, don't bother me person who likes to be alone. Though these changes have taken place, I feel they may just be temporary which is why I will remain on the med. It's truly a pain in the neck to experience such changes and not be able to so to speak "control" them on your own, but in the long run, if it means being healthier and losing the weight that needs to be lost (on me), then for me, it's worth it. Thank God my husband understands all this!!!