Ive just this second finished writing an essay on parkinsons! Parkinsons is notoriously hard to diognose as there is no way of measuring the illness, ct scans and pet scans can be done but the results are not accurate. Parkinsons is due to a degeneration of nerve cells in the brain which begin to slowly affect the muscles of the body. This starts to show first with tremors in the hands and arms. Many people immediatly think that by having tremors is parkinsons, but in most cases turns out to be something else! For e.g I get tremors when I drink coffee, like your friend! But hes doing the right thing by going to a professional, I hope he is ok xx