LONDON - As Susan sits chatting to a nurse in a London clinic, a light tapping sound by her head signals that parts of her brain are being zapped by thousands of tiny electro-magnetic pulses from a machine plugged into the wall.
The 50 year-old doctor is among growing ranks of people with so-called treatment-resistant depression, and after 21 years fighting a disorder that destroyed her ability to work and at times made her want to "opt out of life", this is a last resort.
Until recently, Susan and others like her had effectively reached the end of the road with depression treatments, having tied the best drugs medical science had to offer, engaged in hours of therapy, and tried cocktails of both.
But a renaissance in research into depression prompted by some remarkable results with highly experimental treatments has changed the way neuroscientists see the disorder and is offering hope for patients who had feared there was nowhere left to go.
Their drive to find an answer has taken neuroscientists to uncharted waters - researching everything from psychedelic magic mushrooms, to the veterinary tranquilizer ketamine, to magnetic stimulation through the skull, to using electrical implants - a bit like a pacemaker for the brain - to try and reset this complex organ's wiring and engender a more positive outlook.
Their sometimes surprising findings have in turn taught them more about depression - leading to a view of it not as a single mental illness but a range of disorders each with distinct mechanisms, yet all producing similarly debilitating symptoms.
"The thinking about depression has been revitalized," said Helen Mayberg, a neurologist at Emory University in Atlanta in the United States.
"We have a new model for thinking about psychiatric diseases not just as chemical imbalance - that your brain is a just big vat of soup where you can just add a chemical and stir - but where we ask different questions - what's wrong with brain chemistry and what's wrong with brain circuits."