Why do we have so many diseases running wild?

I have been wondering a lot why so many people are sick with things like depression and Alzheimers. A doctor once told me that they give out more medicine for depression than for any other illness. I personally suffer from it sometimes and so does my wife. Depression is like a huge dark cloud that conceals everything joyful. I have no idea what causes it, and there seems to be no cure. Another doctor told me that depression is like a series of windows going by and they are dark. Finally a window comes by that is lighted and we can see the world, but then here come the dark ones again. That is a good definition of depression. Now if they could just find a cure.... One of my friends was recently diagnosed with Alzheimers, one of my favorite aunts also has it, and a local businessman had to close his store because of it. Why so many? I know of many people that suffer from that terrible mind munching disease. Once again there is no known cure, but the effects of the disease are terrible; both to the victim, and to family and friends. There are of course many more diseases on the loose and I can't help but wonder what causes them. It seems that some of them become more prevalent every year. Could it be the food we eat, or the air we breathe? Maybe we will never know. Maybe we will all become mindless zombies before we can discover a cure. My mind is nearly gone already,,, but tomorrow is Friday!!!!