There are different reasons for a person to go into isolation.
Sometimes it is necessary as when a person with a contagious disease is isolated from others to prevent the spread of the illness; a prisoner or eye-witness to a crime may be isolated to prevent harm to him or her. Sometimes it is by choice as when one chooses a short-term period of isolation to focus on something without distractions or to escape stress. Other times it is beyond one's control as when a person suffers from a mental or neurological disorder; or suffers the consequences of some grievous event.
Depression is one form of isolation. There are several causes of depression yet in most cases many symptoms are similar. It affects one's thinking, behaviour and body functions. I speak from experience; three years of darkness (1997 - 2000).
Besides the feeling of sadness that draped on my shoulders like a heavy dark cloak with a large hood covering my head, hampering my view, almost suffocating me, I was always exhausted, had low energy and yet suffered with insomnia. Panic attacks struck anytime, anywhere, with screaming and wailing. Other symptoms were poor concentration and memory. When I turned to my Bible for consolation, I'd read and re-read one short verse over and over without ability to concentrate on it or to remember it even after immediately reading it. I'd fall exhausted into my bed to toss and turn, and weep the night away.
God seemed far away; a fine vapor that once had form. Hope was a thin worn thread. Even human touch failed to comfort. A hug felt distant and unreal. I felt totally isolated as if I were in a deep narrow muddy pit, surrounded by darkness and demons. From the bottom of the pit, I'd look up in search of a light but my eyes were greeted with more darkness.
My biggest fear was of losing my mind. During one panic attack, my husband asked if I'd like to go to the hospital. I screamed even more as I envisioned being forced into a straight jacket, thrown into a padded cell and forgotten.
I clung with the little strength I had to Psalm 4:8. Although, my heart told me that God had forsaken me because I could not feel His presence, my head said He was with me because He promised in His Word that He'd never leave or forsake me. I thanked Him for that many times.
Today I am alive and well with the days of darkness far behind me because God kept His promise. Hallelujah!