All illness, be it physical or mental, is attributed by Ayurveda to "pragyaparadh".
Babaji says the "the mind exists only when it imagines". Unfortunatly it is this mind, this ego, that causes all our suffering. For the ego to exist it must imagine itself to seperate and distinct from the Divine. So when we humans imagine oursleves different from one another, from animals, from nature, from anything, it follows that we become ill.
Pragyaparadh is a trick of the mind, a mistake of the intellect, the foolish thought that we are seperate. This trick, and illness, can be as a result of a lack of intellect (not knowing any better), the choice to ignore what we know (like smoking even when we know it's bad for us) or simply memory loss.
Let us remember this when our human intellect interferes with nature too much, for example by genetically modifying food, or using chemical fertilisers or growing vegetables in an unsuitable climate. We would not be wise to presume that we know better than nature, better than God. It makes sense then, that we are not very healthy.