In reality, the cause of all illnesses is spiritual in origin. And the major cause is the forgetting of our loving relationship with Krishna, God, the Supreme Personality.
The material illnesses of the spirit soul are those transmitted by karma, that is, those that pass from the body the soul had in its previous life to the one in which it was reincarnated.
The material body is actually the prison of the spirit soul. We have forgotten this, but the fetus in the mother's womb, and then at birth, the being suffers. The body is the source of the suffering of the incarnate spiritual being. The illness that affected our body in our last life, due to our karma and because we have not erased it, will move and reappear in the body we will have in our next existence. We will find ourselves in a new body affected by the same illness.
This is why we often see babies born with serious illnesses, partially paralyzed or even totally degenerative...
God alone controls everything for us. We are all under His tutelage. Even the material body in which the soul is reincarnated does not belong to Him, because it is the property of Lord Krishna. We come into this world with nothing, and it is empty-handed that we will leave it when the time comes. Everything belongs to God. He is not responsible for the misfortunes and suffering we endure.
In reality, we ourselves are responsible for the illnesses, misfortunes, and suffering we endure. The more wicked we are, the more we express through thought, word, and deed hatred, racism, indifference, and coldness of heart toward those who are different from us, the more the mass of our evil deeds increases due to the clouding of our minds, and the more we will be led to suffer in our present life, but especially in our future life.
This is why people sometimes say, “Why this repetition of misfortunes, or what have I done to God to suffer so much?”
Over the course of countless lifetimes, incarnate spiritual beings have accumulated, through their thoughts, words, and actions, a significant amount of harm, culpable acts, or sins that compel them, and today they endure the resulting misfortunes and suffering. Thus, it is through pain or suffering experienced and felt that we diminish and erase our faults.
In this world, human beings are in permanent contact with material energy and, as such, must endure the repetitive cycle of birth, illness, old age, and death.
While there are numerous hospitals and clinics where material illnesses of the body can be perfectly treated and cured, there is not a single hospital center that can cure the material illness of the spiritual soul, which each of us truly is. The true seat of illness is the heart.