It’s often said that depression isn’t about feeling sad. It’s part of it, of course, but to compare the life-sapping melancholy of depression to normal sadness is like comparing a paper cut to an amputation. Sadness is a healthy part of every life. Depression progressively eats away your whole being from the inside. It’s with you when you wake up in the morning, telling you there’s nothing or anyone to get up for. It’s with you when the phone rings and you’re too frightened to answer it.

It’s with you when you look into the eyes of those you love, and your eyes prick with tears as you try, and fail, to remember how to love them. It’s with you as you search within for those now eroded things that once made you who you were: your interests, your creativity, your inquisitiveness, your humour, your warmth. And it’s with you as you wake terrified from each nightmare and pace the house, thinking frantically of how you can escape your poisoned life; escape the embrace of the demon that is eating away your mind like a slow drip of acid.

And always, the biggest stigma comes from yourself. You blame yourself for the illness that you can only dimly see.

So why was I depressed? The simple answer is that I don’t know. There was no single factor or trigger that plunged me into it. I’ve turned over many possibilities in my mind. But the best I can conclude is that depression can happen to anyone. I thought I was strong enough to resist it, but I was wrong. That attitude probably explains why I suffered such a serious episode – I resisted seeking help until it was nearly too late.

Let me take you back to 1996. I’d just begun my final year at university and had recently visited my doctor to complain of feeling low. He immediately put me on an antidepressant, and I got down to the business of getting my degree. The pills took a few weeks to work, but the effects were remarkable. Too remarkable. About six weeks in I was leaping from my bed each morning with a vigour and enthusiasm I had never experienced, at least not since early childhood. I started churning out first-class essays and my mind began to make connections with an ease that it had never done before.

The only problem was that the drug did much more. It broke down any fragile sense I had of social appropriateness. I’d frequently say ridiculous and painful things to people I had no right to say them to. So, after a few months, I decided to stop the pills. I ended them abruptly, not realising how foolish that was – and spent a week or two experiencing brain zaps and vertigo. But it was worth it. I still felt good, my mind was still productive, and I regained my sense of social niceties and appropriate behaviour.

I had hoped that was my last brush with mental health problems, but it was not to be.

On reflection, I realise I have spent over a decade dipping in and out of minor bouts of depression – each one slightly worse than the last.

Last spring I was in the grip of depression again. I couldn’t work effectively. I couldn’t earn the income I needed. I began retreating to the safety of my bed – using sleep to escape myself and my exhausted and joyless existence.

So I returned to the doctor and told her about it. It was warm, and I was wearing a cardigan. “I think we should test your thyroid,” she said. “But an antidepressant might help in the meantime.” And here I realised, for all my distaste for the stigmatisation of mental illness, that I stigmatised it in myself. I found myself hoping my thyroid was bust. Tell someone your thyroid’s not working, and they’ll understand and happily wait for you to recover. Tell them you’re depressed, and they might think you’re weak, or lazy, or making it up. I really wanted it to be my thyroid. But, of course, when the blood test came back, it wasn’t. I was depressed.

So I took the antidepressant. And it worked. To begin with. A month into the course, the poisonous cloud began to lift and I even felt my creativity and urge to write begin to return for the first time in years. Not great literature, but fun to write and enjoyed by my friends on social media. And tellingly, my wife said: “You’re becoming more like the person I first met.”

It was a turning point. The drug had given me objectivity about my illness, made me view it for what it was. This was when I realised I had been going through cycles of depression for years. It was a process of gradual erosion, almost impossible to spot while you were experiencing it. But the effects of the drug didn’t last. By September I was both deeply depressed and increasingly angry, behaving erratically and feeling endlessly paranoid.

My wife threatened to frog march me back to the doctor, so I made an appointment and was given another drug. The effects have been miraculous. Nearly two months in and I can feel the old me re-emerging. My engagement and interest is flooding back. I’m back at work and I’m producing copy my clients really love. Only eight weeks ago, the very idea that I would be sitting at home tapping out a blog post of this length on my phone would have made me grunt derisively. But that is what has happened, and I am truly grateful to all those who love and care for me for pushing me along to this stage.

And now, I need to get back to work. Depression may start for no definable reason, but it leaves a growing trail of problems in its wake. The more ill I got, the less work I could do, the more savings I spent and the larger the piles of unpaid bills became. But now I can start to tackle these things.

If you still attach stigma to people with mental illness, please remember two things. One, it could easily happen to you. And two, no one stigmatises their illness more than the people who suffer from it. Reach out to them.

• A longer version of this article is available on Ben’s blog