Sickness is always caused by sin. Sometimes you can figure out the spiritual cause of your sickness simply by looking into your own heart. On the contrary, sometimes you will have to inspect your entire life and investigate your conscience meticulously in order to find out why you suffer from a certain sickness. It is in your own actions that you will be able to see the real spiritual cause of your health condition: an un-confessed and un-repented sin that, like a morbid scab, causes the sickness of the soul which in turn, in compliance with the unbreakable law of interconnectedness of soul and body, leads to bodily infirmity.
Sickness is a phenomenon of our existence on earth that is familiar to everyone. What is sickness? Why do we get sick? How do we get rid of it?
Speaking of theological approach to this phenomenon, we must be aware of the fact that sickness is nothing other than a decrease in natural human vigor, a discord in his essence, and a change of some sort in his composition, which was created by God. The human was called from non-existence into being by the Divine Love, and he was created perfect. Therefore, there was no place for sickness in his body.
However, when humans transgressed God’s will and trespassed the commandment given to them by their Creator, their sinful actions introduced a distortion into the world, and their nature underwent a transformation that can be most aptly characterized with the word “corruption”, i.e., a rift, a discord. This corruption resulted in sicknesses and suffering. Therefore, sicknesses and bodily weaknesses result from the Fall. It is by no means a coincidence that both bodily suffering and sinful habits of one’s soul are called “passions”.
This is how we can explain the spiritual mechanism of sickness more easily, and give an answer to the question, “Why do we get sick?” When a person voluntarily chooses to trespass God’s commandments and turns his back on the Lord who is the Source of all life, he gets on a different track. As he moves along this track, which leads to dying, he will inevitably encounter sicknesses, sorrows, and ailments that are the harbingers of death.
A sickness, allowed by God’s Providence, is nothing other than a means to teach a person who defected from God’s Truth. This is how C. S. Lewis, a British author and religious thinker, treats suffering. His thoughts about it are remarkably concise: “God whispers to us in our pleasures, speaks in our consciences, but shouts in our pains. It is his megaphone to rouse a deaf world.”
Anyway, if the root of one’s sickness lies in the sin, one must direct his efforts to take that root out first. We Orthodox Christians can and should use medicines and seek doctors’ advice; nevertheless, we must never neglect spiritual treatments, i.e., the Sacraments of Confession and Communion, the Sacrament of Unction, and first of all, prayer to the Lord and his saints.