At the time, in 2004, Chibanda was one of only two psychiatrists working in public healthcare in the whole of Zimbabwe, a country of over 12.5 million people. Both were based in Harare, the capital city. Erica, on the other hand, lived in a remote village nestled in the highlands of eastern Zimbabwe, next to the border with Mozambique.
Erica had passed her exams at school but was unable to find a job. Her family, she thought, wanted her only to find a husband. To them, the role of a woman was to be a wife and a mother. She wondered what her bride price might be. A cow? A few goats? As it turned out, the man she hoped to marry chose another woman. Erica felt totally worthless.
Erica and Chibanda met every month for a year or so, sitting opposite one another in a small office at the hospital. Chibanda prescribed Erica an old-fashioned antidepressant called amitriptyline, hoping that after a month or so, she might be better able to cope with the difficulties back home in the highlands.
You can overcome some life events, no matter how serious, when they come one at a time or in a small number. But when combined, they can snowball and become something altogether more dangerous.
For Erica, it was lethal. She took her own life in 2005.
Today, an estimated 322 million people around the world live with depression, the majority in non-Western nations. It's the leading cause of disability, judged by how many years are 'lost' to a disease, yet only a small percentage of people with the illness receive treatment that has been proven to help.
In low-income countries such as Zimbabwe, over 90 per cent of people don't have access to evidence-based talking therapies or modern antidepressants. Estimates vary, but even in high-income countries such as the UK, some research shows that around two-thirds of people with depression are not treated.
As Shekhar Saxena, the Director of the Department of Mental Health and Substance Abuse at the World Health Organization, has put it: "When it comes to mental health, we are all developing countries."
Soon after Erica's death, Chibanda changed his career plans. Instead of pursuing his original goal of opening his own private practice -- a role that would, to an extent, limit his services to the wealthy -- he founded a project that aimed to provide mental health care to the most disadvantaged communities in Harare.
"There are millions of people like Erica," Chibanda says.
Discovering Zimbabwe's high levels of depression
In the early 1990s, Harare -- nicknamed the Sunshine City -- appeared to radiate positivity. A survey from the city reported that fewer than 1 in every 4,000 patients (0.001 per cent) that visited the Outpatients department had depression.
In comparison, around 9 per cent of women in Camberwell in London were found to be depressed.