I wonder why there is an increase, perhaps we should look at the causes. Like environment, ie overcrowding, happiness etc. If peoples everyday life is not good - you will get an increase in mental health. So if peoples living standards improve so will mental health (that's were the problem is and there is a lot wrong).
There is a need to prevent mental illness. try taking the advice of scientists like Prof. Philippe Grandjean , as to the main causes of mental,illness.
To create the causes and then seek to cure the illnesses , is a totally bizarre concept of how to create good health, whether mental or physical