I consider myself a person of generally happy disposition, with few anxieties, who enjoys the company – of both men and women – and who is fortunate to have stumbled upon a career that he loves.

It was not always that way. I had a dark period, starting when I was seventeen years old when despair gripped me and the world seemed hopeless. Harbouring all my anxieties inside me, I was sure this darkness would never lift. Luckily, it did. It began to improve, after about a year and a half, and eventually lifted totally. It was embarrassing for me to have such an unexpected episode and I did not feel like speaking about it. I did not tell my friends, and I did not tell my parents because it would have been too distressing for them.

I had led a sheltered, happy childhood in Kolkata, growing up in a household with parents and four elder sisters who doted on me. My father was an introvert and his love for his children had few behavioural manifestations. It was noticeable that every time my sisters or I were unwell, even with a common cold, my father spent longer than usual in the office. My mother laughed and told us he could not bear to see his children unwell, and so opted for a cowardly vanishing act (making frequent phone calls from his office to check how we were doing).

Growing up, I had a large clan of relatives spread through the city, who dropped in with a frequency that would shock a modern household. After I moved to the US, I remember one of my American colleagues, curious about Indian culture, asking me if my parents knocked on my bedroom door before coming in. Not only did my parents not knock, nor did our neighbours, Mr and Mrs Ghosh.

My father grew up in a poor household that plunged into even greater poverty after my grandfather died prematurely. My father struggled to earn a meagre income to help his mother and eleven siblings and got a law degree quite late in life by studying in the evenings. It was totally unexpected that he would do as well as he did as a lawyer. By the time I was old enough to have memories, it was a household with multiple staff, drivers and helping hands, loyal to us in a rather feudal way. In 1969, when I finished high school and was getting ready to continue with the sheltered life of living with my parents and being driven every day to college, my mother came to me one day and said my father wanted to know if I would agree to go and study in Delhi, at St Stephen’s College. It would just be three years away from home. It was obvious from the tone that my father was urging me to do so. This was a bolt from the blue. St Stephen’s College was India’s premier undergraduate institution, but I had never thought my parents would want me to leave home until much later.

In retrospect, this was one of the wisest moves in my life. My father was a worldly philosopher. Though my departure would be painful to him, he had calculated that I needed the jolt of being on my own in order not to become a vegetative homebody. I agreed to apply to St Stephen’s.

There was a touch-and-go moment during the interview when I lied and said I wanted to do economics because I loved the subject, and the chair of the department, Mr NC Ray, asked me what I had read in the field of economics. I could not say I had developed the love from having read nothing. I fumbled, and then recalled that one of my school textbooks had a half-page on “Marx’s theory of surplus labour and why it is wrong”. I had studied at St Xavier’s, a Jesuit school in Kolkata, and our missionary moral science teacher had made us learn that half-page by heart. I told the interview board I had been reading about Marx’s theory of surplus labour and had reached the conclusion that it was wrong. I spoke for about five minutes elaborating on this. The interview board was impressed by my knowledge and I was impressed by my capacity to speak without knowledge.

And so, in July 1969, at the age of seventeen, full of trepidation, I left home for the first time to live in another city. I moved into my dorm at St Stephen’s College, in Rudra South. I met students much more boisterous than me, who had been educated in westernised boarding schools in different parts of India. The novel setting, being away from home and a feeling of inadequacy with these westernised classmates did create anxieties, but in ways that were normal, at least during the first three months.

After returning to college from the two-week October break, the plunge began. To this day, I do not know quite what happened to me. Was it triggered by moving out of a home where I felt totally, absurdly protected? Was it caused by a feeling of inferiority – a concern that I was not up to the mark with such smart classmates? Was it a specific psychological problem which had a name? Were there others who got it? Is it known what causes it?

For me, now, this is a matter of pure intellectual curiosity. In case one of my readers has an answer, let me fill you in with one or two details. One marked feature of this anxiety or depression or melancholia – I do not quite know what to call it – was its clear daily routine. I would wake up feeling more or less fine, then sometime in the morning, the anxiety would start, building up through the day, becoming acute by late afternoon. Then, as night descended, it would begin to ease.

As the months passed, the daily interval of calm, from night to morning, kept getting shorter. This growing anxiety and depression were accompanied by a loss of interest in everything. It had no daily cycle; it was persistent. I had no ambition; I no longer cared for any of the things that had been dear to my heart. It was a cause of genuine despair that I appeared to be living with no purpose whatsoever.

I read that John Stuart Mill had a similar episode in his life when he was twenty. Normally, I would have been thrilled to find that I had something in common with John Stuart Mill, but at the time this too meant nothing. I continued to attend classes, had lots of friends, genuine and close. No one guessed what I was going through. After a year, I was fully reconciled to the fact that this pall of darkness would never lift from my life.

But it did. I do not know what got me out of it. I did see a psychiatrist in Kolkata in the middle of this, the only time in my life when I have done so. A well-read, cerebral person, he talked about Freud, Jung and others, and said that a lot of human problems arise from our ascribing too much importance to one aim in life – sex, money or fame. He said that, for people of my age, a lot of psychological stress arose from latent sexual anxiety. He blamed Freud for this. Freud’s emphasis on the sexual origins of our psychological problems became self-fulfilling. The psychiatrist argued that once we realize there is no single purpose or target in life that takes precedence over the others, it takes a huge load off our shoulders. I don’t know whether his counselling helped me directly, but I remember his intelligent, humane conversation fondly.

The start of the lifting of the depression – I call it depression for want of a better word – from around the age of twenty was quite baffling, since by then I was reconciled to a life in its shadow. After another year or two, it was gone. I did not speak about it for years. Partly out of shyness, partly a fear that, in talking about it, I might rekindle the dormant genie.

I do not know what made the melancholia go away and whether, like some episodic virus, it would have gone away anyway, no matter what I did. But there is one strategy which I began using around this time, which has stood me in good stead: reasoning with myself, and trying to be completely honest when doing so. Since I did not have access to antidepressants – almost no one in India at that time did – reasoning inside my head was my only ammunition. Whether or not it helped me specifically with my period of crisis, I emerged with the belief that honest, ruthless reasoning inside your head is one of the most powerful and underutilised recipes for happiness.

Excerpted with permission from Reason to Be Happy: The Unexpected Benefits of Thinking Clearly, Kaushik Basu, Torva.