I believe that I completely understand your confusion and the reasons for it. For instance:

My body stopped working and I fell headfirst into a depression the depths of which I didn't believe existed. About the same time, I was diagnosed with a physical ailment called myasthenia gravis. Myasthenia gravis is Latin for "grave muscle weakness". So how exactly was I suppose to be able to tell the difference between the "I can't get out of bed" because of a major depressive disorder (which I had never experienced before) or the "I can't get out of bed" because of the "grave muscle weakness" which I had also never experienced before? In fact, was I even depressed? Or was it all the myasthenia gravis? How could I tell?

Turns out, I couldn't tell and as a result, I laid in bed and nurtured the depression from hell for years thinking it was the myasthenia gravis. Since the way I address each issue (depression and my myasthenia gravis) is different, it was important for me to know which was which. Pushing through a myasthenia weakness can cause death. Anyway, knowing which was which allowed me to better understand and care for myself.

So, tough answer: You don't know who to trust and you're not going to until your are able to determine for yourself what's related to what - and even then, you could be wrong. We do the best we can.