[mikeash]

Attitude is proven to have an effect on cancer remission rates. Yet we still call it a disease and say that it killed you, not that you selfishly killed yourself due to not getting better.

You have some control. Far less than the "suicide is selfish" idiocy assumes.

[dreamdu5t]

So you're claiming suicide is caused by a biological mechanism? That once we identify that mechanism, we could prevent suicide?

Great, maybe that's the case. However, there's no more evidence for that than the assertion that suicide is a choice.

[Mz]

There is some evidence that brain chemistry is influenced by diet and dietary changes can help with depression. For example: http://www.mayoclinic.org/diseases-conditions/depression/exp...

That fits with my experience. I have to be very careful with peanut oil, for example. It does terrible things to me.

So, in short, it is possible that depression and other mental illness has biological roots. There are also social factors and other factors, but in some sense mental illness may well be a medical illness.