Kittycat is right about Topamax (Dopamax). Usually if taken at a therapeutic dose, it causes what is called cognitive slowing. (The mind's capability and speech is slowed down, there can be confusion and memory is affected, too).
Also, even many pdocs are unaware that bipolar depression is very, very different from clinical depression in a non bipolar patient. It in itself causes the congnitive slowing, only it is called psychomotor slowing, which means not only is the mind not working at full strength, neither is the body. That's where the muscle weakness and/or extreme physical fatigue comes in. That is what can make you feel trapped in your mind and body, like it's a prison. (Can't get out of bed). I have been there too and wanted to die. People, even some docs, don't realize that, because the criteria for depression is the basic formula and is usually what is listed for bipolar, too. People would just have to be in that dark place to even imagine the misery.
Stress and anxiety do not cause this condition, if anything they speed up the mind. They can still sometimes cause some fatigue, tho, but not to the extent of full blown depression.