First of all, thank you for your desire to understand. People like you are rare - I've been battling this illness my whole life, and I don't know that I've ever encountered anyone who was truly curious to understand what it feels like.

As some folks have said, depression is often a state of bleak numbness and abysmal apathy. Not always though. Sometimes, it takes on a ruthless, malevolent form. I've had bouts which I can only describe as feeling like a gnawing, aching, searing agony that permeates my entire being. There's a visceral component to the pain of severe depression and when it doesn't let up for a long period of time, that's when suicide becomes a real danger due to the desperate need for relief.

I've never come across a more accurate and vivid description of depression than what the author William Styron wrote about his own battle in his memoir, A Darkness Visible. Here are a few selected snippets:

The gray drizzle of horror induced by depression takes on the quality of physical pain. But it is not an immediately identifiable pain, like that of a broken limb. It may be more accurate to say that despair, owing to some evil trick played upon the sick brain by the inhabiting psyche, comes to resemble the diabolical discomfort of being imprisoned in a fiercely overheated room. And because no breeze stirs this caldron, because there is no escape from this smothering confinement, it is entirely natural that the victim begins to think ceaselessly of oblivion.

There is a region in the experience of pain where the certainty of alleviation often permits superhuman endurance. We learn to live with pain in varying degrees daily, or over longer periods of time, and we are more often than not mercifully free of it. When we endure severe discomfort of a physical nature our conditioning has taught us since childhood to make accommodations to the pain’s demands—to accept it, whether pluckily or whimpering and complaining, according to our personal degree of stoicism, but in any case to accept it. Except in intractable terminal pain, there is almost always some form of relief; we look forward to that alleviation, whether it be through sleep or Tylenol or hypnosis or a change of posture or, most often, through the body’s powers of self-healing, and we embrace this eventual respite as the natural reward we receive for having been, temporarily, such good sports and drought sufferers, such optimistic cheerleaders for life at heart.

In depression this faith in deliverance, of ultimate restoration, is absent. The pain is unrelenting, and what makes the condition intolerable is the foreknowledge that no remedy will come—not in a day, an hour, a month, or a minute. It is hopelessness even more than pain that crushes the soul. And so the decision-making of daily life involves not, as in normal affairs, shifting from one annoying situation to another less annoying— or from discomfort to relative comfort, or from boredom to activity—but moving from pain to pain. One does not abandon, even briefly, one’s bed of nails, but lies upon wherever one goes.

The pain of severe depression is quite unimaginable to those who have not suffered it, and it kills in many instances because its anguish can no longer be borne. The prevention of many suicides will continue to be hindered until there is a general awareness of the nature of this pain. Through the healing process of time—and through medical intervention or hospitalization in many cases—most people survive depression, which may be its only blessing; but to the tragic legion who are compelled to destroy themselves there should be no more reproof attached than to the victims of terminal cancer.