Positive thinking . . . And posture?

I had a very interesting discussion with my Alexander Technique teacher this afternoon during my session. During a recent relapse I have felt my core become weaker -and consequently am aware that I have been slumping a bit. When telling him this, he asked how my depression was during the relapses - he  has been noticing a trend with his clients that they often had both depression and a slumping posture.
I certainly notice myself slumping when I am having bad days and a great email/call which engages and enthuses me does make me sit up better for a while!
I wonder if any one else has noticed their posture in relation to their mood? It is an interesting concept, and possibly quite important in patients with long term conditions such as back pain that are often accompanied by depression.

Update: In the esteemed scientific publication that is Red Magazine, a study from San Francisco State University is discussed - in their study, they found that getting students to walk tall (and fast) improved their energy levels and made them feel more cheery. As Dr Pepper explained, "your brain affects your body - but your body equally affects your emotions."
I do think there is a link, whether associative, resultant or causative! If I had time, I'd love to research this area more...