The first time I went for a run as an adult, I was at university and had been deeply depressed for several months. I managed a minute before I had to walk, but, I told myself, a minute was a start. I went every day and, as the weeks passed, I ran further, for longer. The impact was immediate – even after that first jog I felt a rush of achievement, of hope. And it was cumulative: every run that followed made me feel stronger, physically and emotionally. Then, one day, many months later, I realised I was not depressed any more.

As the years passed, I gradually branched out from short jogs into runs of more than two hours. I went to circuit classes and step classes, interval training and personal training, core sessions and legs, bums and tums sessions. I dropped two dress sizes and developed stomach muscles.

I would often return home in some sort of post-workout orgasmic bliss. The endorphins did something magical to my brain; as I jogged past trees, people, buildings, I felt so intensely moved that tears pricked my eyes; I felt like crying with the joy of being alive. I was high – a socially acceptable, doctor-recommended, perfectionist-approved high.

I became an exercise evangelist. It makes me nauseous to remember how I would bang on about it to anyone who would listen – and anyone who wouldn’t. I believed exercise was a cure-all. It had made me happier, fitter and slimmer, and I tried to convince everyone that this could be true for them. I am ashamed of how I spoke without listening to friends I tried to cajole into my exercise-filled lifestyle. I thought I knew what worked for all of us.

The problem was that it was never enough. Although my depression was gone, some feelings of anxiety lingered. I would regularly wake up with a pain at the back of my throat and a vague sense of jittery doom that sucked all the peace and pleasure from my life. I blamed myself for these feelings. I told myself they came because I had not done enough exercise – so I would do more exercise.

Then, one evening in a core class, I felt a twinge in my lower back. It wasn’t too bad, so I carried on. The next morning I awoke in agony. I consulted a physiotherapist who told me it would take two months to heal; in fact, it took closer to a year.

I had to go cold turkey, exercise-wise. It was like waking from a dream. Suddenly, I saw how extreme and unbalanced my behaviour had become. I began to question the way in which I had used exercise to regulate my mental health, as if it was mood medication with no side-effects. If you tell an anxious person to exercise, they might well do it in an anxious way. I had co-opted everything in my life into my swirling anxiety, including exercise, which was supposed to be my way out of it.

As that year came to an end, I began having psychoanalytic psychotherapy, which is pretty much the opposite to running away from anxiety. For a start, you are lying down on a couch. But, more than that, it is a space where it is sometimes possible for me to describe my anxiety and get the measure of it; to try to work out where it comes from and why. As I say out loud whatever images and thoughts come to me, my therapist makes interpretations about what she thinks is going on in my mind, the unconscious processes and assumptions that she can glimpse in my communications, but which I cannot understand alone. I am discovering more about these anxious feelings and where they might originate, about the unconscious rulebook I seem to have knocking around in my mind, telling me what is right and what is wrong. I am coming to see how punitive we can be with ourselves without noticing.

My back has healed, but I have not gone back to such obsessive exercising. I do it two or three times a week: one run, a pilates class or two, plus regular walks. This level feels right for me, at the moment anyway. I still have bad days, but many more good ones, and the bad days seem more bearable.

The benefits of exercise for mental health are proved and much discussed. I’m not denying them. But I do think that, for many, the story is more complex. It took many years for me to realise that exercising is not the answer to everything; that running was not a solution to my problems, but a means of not facing them. I wonder if I have done a straight swap of exercise for therapy, the running track for the couch, switching my belief from one cure to another – but at least I now have a space to think about that.