"Do you not know that your body is a temple of the Holy Spirit, who is in you, whom you have received from God? You are not your own; you were bought at a price. Therefore honor God with your body." (1 Corinthians 6: 19-20)
Depression may have physiological or physical causes (not just mental/psychological). Our psychological and emotional health is influenced by the wellness or functioning of our physical body. When something is amiss physically, perception and feelings are usually affected in some ways.
Doctors call it the "biochemistry" of depression. There are at least two chemicals in the brain that need to be monitored -- serotonin and noradrenaline -- that are known to affect emotional states such as depression and mania. Scientific research indicates that low levels of these brain chemicals, interacting with heredity, hormone levels, and electrolyte balance, tend to produce depression.
This is the reason why I advise those experiencing depression (especially the severe ones) to undergo complete medical examination before or during actual psychotherapy sessions. Such will provide information whether physical irregularities are involved in the depression and not just mental, emotional, or spiritual aspects.
For some, anti depressant drugs can aid in healing depression. I have a word of caution though. Almost all drugs have "side effects." These are undesirable reactions/negative effects on the body or some of its organs which are not central to the primary purpose of the drug taken. Some drugs are known to produce some times upset stomach (e.g. aspirin), pain in other parts of the body, or greater depressive states as a side effect in persons who are predisposed.