From now on, when someone who hasn’t experienced clinical depression and anxiety asks me what they feel like, I won’t have to resort to florid comparisons. I’ll say: “Remember when the Covid-19 pandemic hit town?” and they will understand. Except that for people with depression and related conditions, the present moment is one of escalated distress. For this is a double crisis, of physical and mental health, and those living the psychiatric challenges need not only acknowledgment but also treatment. I have had dozens of letters and Facebook messages from people who are anxiously upping their doses of antidepressant and anxiolytic medication.

My depression and anxiety share a lot of territory with how most other people feel now: fear of getting sick and dying, fear of losing people I love, fear of unpredictable shortages and economic disaster. Others worry whether their cough is a symptom of Covid-19 or just an allergy. I am in the sizeable part of the population who must seek to distinguish between ordinary fear and the beginnings of a breakdown. I’ve had to alert the doctors who oversee my mental health that I am Code Fragile and will count on them to help me discern whether I cross over from ordinary unhappiness into neurotic paralysis. I have had to cancel my planned withdrawal from a medication that makes me sleepy and fat; lowering my dose would leave me unsettled for a spell, and that’s more than I’m up for now.

In March, I experienced the whole panoply of Covid-19 symptoms: a racking cough that kept me up all night but was not accompanied by any congestion, a fever that soared over 103F (39.4C), aching joints and trouble breathing into lungs that felt like they couldn’t expand all the way. Despite pulling every string I could muster, I was unable to get a test. My doctor diagnosed flu at first; when I couldn’t breathe, I had a chest X-ray and he diagnosed pneumonia. I took Tamiflu, then azithromycin. I quarantined myself at home and rigidly kept distance even from my husband and our son. Now I am fine, and nobody who was in contact with me has been infected. But the unavailability of tests was terrifying and the circumstances seemed to invite in psychic decay.

Quarantine is the oldest medical technology out there: isolation of the sick dates to the ancient world. While it protects those who are not ill, it is toxic for the patients, who show elevated rates of depression, anxiety and post-traumatic stress disorder. Physical recovery is slower for those cut off from friends and family. Quarantine is often necessary for people with incurable or highly contagious infections such as MRSA, Sars or H1N1, but it comes at a terrible cost. No one wants to die alone.

Sheltering inside when you have no symptoms, however, is essentially a new phenomenon: it happened in Toronto during the Sars outbreak of 2003, and many authorities felt its costs far exceeded its benefits. Richard Schabas, formerly Ontario’s chief medical officer of health, wrote: “In the unlikely event of another Sars outbreak in Canada, public health officials should quarantine no one.” His intent was not to dismiss the physical dangers, which were real then as they are now, but to illuminate the psychiatric ones.

This is a bizarre time, and people are dying – but people are always dying, I remind myself. One acquaintance of mine died yesterday of the virus, and another has died tonight of cancer. The first death terrifies me; the second merely saddens me. Social distancing is staunching the proliferation of new cases, but some of us are overreacting and some of us are underreacting and no one knows which are which; it is unlikely that many have hit the sweet spot of appropriate caution. The need for caution must also take into account the effect of isolation on mental health, as anyone knows who has seen The Shining or Cast Away. When I lived with the Greenlandic Inuit, I found that their high rates of depression and suicide were tied not to the sunless winter, but to the intimacy it forced. Whole families gathered in small houses and were stuck with one another and no one else for months because it was too cold and dark for anyone to leave or visit. Emotional repression was the natural consequence, and it was calamitous.

I was on holiday with my extended family when the idea of social distancing was introduced into the popular vocabulary, and had to come home early when the place we were visiting sealed its borders. I have since been sheltering with my husband, my son and my father-in-law in upstate New York. Two weeks ago, I set out for New York City to pick up our family dog, get my 10-year-old son’s school books and pay some bills. I didn’t recognise the empty city where I had grown up. I perched in my office thinking grimly that I would never be able to live at home again. I lie awake with my mind running and have to remind myself that this is how my mind runs when it is in bad shape. I saw my elderly father today and we met outdoors and kept a 6ft distance. I suffered anew the collapse of that feeling of safety he had created in earlier crises, a role he cannot fill at nearly 93. Intellectually I know that my father could never have solved this crisis; that I will eventually live at home again; that I am probably safe in the house upstate. It is my project to keep up a good face for my son, and it is utterly exhausting, sometimes impossible and profoundly redemptive.

UK poll finds young people's mental health hit by coronavirus Read more

Yet, as always, at the bottom of depression’s box there is hope. The very feeling of frailty gives me a window into the suffering of friends who are waiting out this terror by themselves. The feeling of isolation awakens me to the ongoing plight of older people who are alone all the time. I feel singularly well-placed to comfort those who are taking their first deep plunge into depression. I can help them assess what is pathological and treatable.

I am in pretty good shape. I had a bad depression two years ago, and I feel much better now, which seems bizarre given how much worse things are than they were then. I am not all by myself, and I have not lost my job. I don’t feel sorry for myself and I don’t think I am suffering more than others are, but I am suffering a bit differently. The second-guessing all the time is burdensome. Am I proportionately or disproportionately having these particular feelings in this particular moment? Depressives find that our intense sadness and fear easily become intense depression and anxiety. People with pre-existing pulmonary illnesses drop dead of this thing. People with previously existing mood disorders will die of it, too, if mostly in a slower and less obvious ways.

• Andrew Solomon is the author of The Noonday Demon: An Atlas of Depression