For more than a decade I've been trying to understand what's wrong with me.

I know I'm insecure. I hate confrontation, I lack discipline, and I have ugly legs. I'm also terribly out of shape, and I ought to do something about my hair. What I don't understand, though, is why what I thought was a sensitive disposition became in 1989 a diagnosis of depression. Why, after a troublesome but certainly not deadly case of shigellosis, did I end up in a psychiatrist's office, of all places, panic-stricken and feeling close to physical and mental collapse? And more than ten years later, what do four little pills have to do with it? Why should they make such a difference in the way I choose to view the world and who I am?

I suffer from depression. So the doctor said. So he continues to say. These days it's getting easier to believe him and take the medicine I have, but it's taken a while to get here. When the doctor first told me I was depressed, I was puzzled. Of course I was depressed. I was often depressed, loads of times, ever since I first learned the word. But I certainly wasn't depressed. It would have been nice to blame all my problems on an authentic mental condition, but I didn't have one. I merely was finding it hard to connect in the world after being hit with dysentery and its aftereffects. I was no longer interested in bouncing back.

And while I fully respected the intelligence and expertise of the doctor I began to see, he could base his diagnosis only on the subjective information I was giving him. It wasn't his fault he thought I was depressed; it was mine.

A distinguishing feature of my depression has been the trouble I keep having with who should decide when depression is an illness, not a frame of mind. How can someone who's outside my mind clearly determine what's inside it, if all he has to go on is what I tell him? What if I've simply exaggerated my emotions and let them get the best of me? What if I'm not trying hard enough?

What makes a doctor so confident about his diagnoses, anyway? The Diagnostic and Statistical Manual of Mental Disorders? It didn't matter to me that the DSM I consulted spelled out depression with a host of symptoms and arranged them with codes and categories. I could never find all of me in there on any one of many confusing pages. Was I experiencing a major depressive episode, or was I hosting a major depressive disorder? Was it a major depressive disorder, single episode, designated 296.2x in the manual, or major depressive episode, recurrent, designated 296.3x?

If so, how severe was it? In place of "x," should I pick number 1 for mild, 2 for moderate, 3 for severe, without psychotic features, or 4 for with them? Number 5 if in partial remission, or 6 if in full? Or should I choose 0 for unspecified?

I still wasn't sure. Was my condition 300.4, dysthymic disorder? Chronic major depressive episode? Or major depressive disorder, in partial remission? How about code 296.90, mood disorder not otherwise specified? Depressive disorder not otherwise specified? It was hard to see where to submit my résumé to find out which depression I was qualified for. DSM has its purpose, but as I read it, it became just another place where I didn't fit in.

Unfortunately there is no blood test for depression. Nothing about it shows up on an x-ray. There is no parasite involved, no signature rash. Nothing at all to show a doubting Thomas like me, who wanted to see it to believe it. The depression I experience never feels like an illness. To me, it's a bad attitude, a deficiency of willpower, and something I brought upon myself. It is a weakness I'm ashamed of.

When I'm "depressed," this is how I reason: "I'm not nauseated. I don't have a fever. I can walk and talk and eat and read and shout hallelujah if I have to—I just don't want to. Which means I'm the one who's uncooperative. It's obviously my fault—don't go blaming it on some disease. Maybe other people have this disease, but not me." It never occurred to me that maybe all of my objections about having depression were being fueled by it.

Real depression, in my mind, was validated by tragedy, heartache, financial woes, abusive parents, a family death—the powerful blows life can deliver, not a few slaps on the wrist. It seemed to me one had to earn the right to call herself depressed. My loneliness and despair came from character flaws within me, not from tragic circumstances surrounding me, and though I often wished the doctor would come to my rescue, I knew I was no damsel in distress. My sad dragon was of my own making, visible only to me.

I'm told that one of the reasons it's hard for some depressed people to recognize the symptoms of their illness is precisely because they suffer from it. What we are familiar with, we cease to see, and what we hear when the medical profession attempts to enlighten us about our condition unfortunately leaves us in the dark:

"Why am I depressed?"

"Because you are experiencing excessive feelings of sadness, guilt, and worthlessness."

"Why am I having these excessive feelings?"

"Because you are depressed."

This explanation reminds me of a Möbius strip, or the title of a Pirandello play:It Is So! (If You Think So.) You Are Depressed! (If a Psychiatrist Thinks So). I think I was born with the tendency to think pessimistically and be overly sensitive and anxious. At what point did my temperament metamorphose into symptoms of a disease? Are they distinct, or are they one and the same? I certainly had been sick before without being told I was depressed, so why would I suddenly fall apart in the 34th year of my life to a point where I now warranted that diagnosis?

Because depression truly feels like something I should be able to control and because it's a way of thinking I can't remember not having, I've resisted it as a legitimate diagnosis. Depression is who I am, not what I have, because that's a simpler explanation than trying to understand how both distinctions might be true. It's always been hard to believe it's really not my fault, any more than having diabetes would be. Like the song says, don't worry, be happy. Isn't it supposed to be that simple for everyone?

Nothing is simple when you're depressed. Waking up to face a new day is hard. Getting something—anything—done is hard. Going out into the world is hard. Communicating, thinking, and deciding, keeping up with personal hygiene—it all seems so pointless. Hope is impossible. Years ago I remember being struck by this statement: "That life is worth living is the most necessary of assumptions and, were it not assumed, the most impossible of conclusions." How exactly true, I thought. Surely the author knew what I was going through and was himself no stranger to despair. Making that most necessary of assumptions and resisting the urge to take leave of the world can be very hard indeed.

Over time I've received a fairly broad range of medications: Prozac, Nardil, Anafranil, lithium, Paxil, Zoloft, Serzone, Wellbutrin, and Celexa, along with Cytomel, Buspar, Ritalin, Klonopin, Depakote, and Neurontin, in various combinations. Many times I stopped taking them, because I knew I wasn't depressed, I had misled the doctor, I had exaggerated my pain, I wasn't trying hard enough, I was a wimp, I was stupid, it was all my fault. I believed all the pills I was taking were behind my so-called depression, because their possible side effects are also symptoms of the very disease they are meant to alleviate.

Interestingly enough, I never stopped going to therapy. For someone who insistently maintained that she was not depressed, I kept my appointments no matter how awkward or embarrassed or undeserving I felt. I called myself a gnat, a burr, a barnacle, and a parasite, but still I kept going—twice a week for the first seven years. The few times I managed to cancel appointments in order to show myself I was fine, I was normal, I was not going to let myself need anyone, in fact I became self-destructive and inconsolable. The doctor was like a life preserver to me, the only safe thing I could cling to as I struggled to keep my head above water, caught in the terrible ocean called Life. He was one of few people who knew about my depression, and probably the one person on Earth who knows the extent of my suffering. No amount of medicine could possibly take his place, and I am fortunate that the insurance companies did not have final say over whether I could remain in therapy.

Currently I continue to keep my appointments. I take three purple tablets and one white oval pill every day. I'm no longer certain about the concept of willpower, or if the antidepressants I take have only a placebo effect and are therefore unnecessary. I have to wonder how many other people there are who don't allow themselves to consider the possibility that they may truly be depressed. I never take my future for granted, or underestimate the power of despair. Sometimes I'm still blue, but then again, I'm still here.

Ms. Henry, who is writing under a pseudonym, lives in Virginia. Send correspondence to her in care of Psychiatric Services, 1400 K Street, N.W., Washington, D.C. 20005. Jeffrey L. Geller, M.D., M.P.H., is editor of this column.