It is incorrect to say that depression is not an illness or that alcoholism is not an illness or that same-sex attraction is not an illness. The standard definition of an illness is any condition which upsets the homeostasis of a system. There are spiritual illnesses and physical illnesses. I suppose one could even say that there are mental illnesses, although their crossover into spiritual illnesses is profound.
Calling something a mental illness will not give one license to say that we are not spiritually responsible for it and for the things that we do because of it. This is the way of the world nowadays. A person says I have depression and therefore since it’s an illness I’m not responsible for it. A person might say I’m same-sex attracted and I was born this way, and since the world teaches me that I should act on my impulses I am not responsible for them and they must not be sins. This is wrongheaded thinking.
It is always good to think humbly about ourselves and blame ourselves. The world doesn’t understand this, but the Orthodox church, with our wonderful ascetic theology, does understand this. Our prayers make this very clear, and ignorance regarding them is a terrible spiritual problem for many Orthodox Christians.
Any Christian who has great problems, weaknesses or sins must improve his prayer and struggle, or else all other solutions will be ineffective or less effective, or even harmful. Look to yourself if you are depressed, or have SSA, or an addiction. Could you pray even a little bit more? Confess more? Fast at least a little bit more? Struggle to be on time to liturgy, come to the evening service at least sometimes? Read the prayers in the prayer book, and try to learn from them? Pray for a person who has harmed you? Quantity is not important, but EFFORT is. It is almost always true that we can make more effort. Something is always better than nothing.
Blaming ourselves does not mean that we have a terrible poor self-concept about ourselves. Blaming ourselves means taking responsibility for all of our actions and thoughts, and AT THE SAME TIME, with a warm hope in God, Whom we know will help us, because He loves us and is merciful.
Sin is anything that is not like God except for the blameless passions. The blameless passions are things like the need for sleep or food. We have those needs because we are in the flesh. In the next life, we will be in the flesh but not have those needs. All of those needs are signs that we are not yet perfected.
Depression is certainly an illness, and it certainly can be treated with medications in some cases. It is always an incomplete treatment and even a dangerous treatment to only use medications and not also to pray, and struggle to follow the commandments, and understand that our spiritual actions are part of our healing. Our healing for anything is through God because of His love for us.
It is a significant mistake to consider the depression is only a biological illness and not also a spiritual one. When one calls something a mental illness generally what they mean is that there is some biological reason for the illness and that morally the person is completely blameless. Sometimes they believe there is only a biological reason for the illness. The former is often true, but the latter is never true.
Nothing we do should be done without the spirit. That includes taking medicine or getting medical treatment. We are composite creatures with a body and a soul. When we are ill , the body and soul both need attention.
Priest Seraphim Holland