Medical device company Flow has announced that it has raised $1.5m in an investment round led by Khosla Ventures to tackle the world’s most urgent mental health challenges, such as depression.

The investment will be used to support the company’s European rollout, and help introduce Flow to healthcare clinics, and fund clinical studies.

The treatment is a physical and behavioural, at-home solution for depression which comprises a portable brain stimulation headset and therapy app. It combines clinical psychology, neuroscience and innovative technology including machine learning.

People diagnosed with depression often have lower neural activity in their left frontal lobe, the part of the brain controlling important cognitive skills including emotional expression. The Flow headset uses transcranial direct current stimulation (tDCS), a form of neurostimulation that delivers constant, low direct current via electrodes on the head to stimulate and rebalance neural activity in this area.

Randomised controlled trials published in the New England Journal of Medicine and the British Journal of Psychiatry showed that brain stimulation, of the type used in the Flow headset, had a similar impact to antidepressants but with fewer and less-severe side effects.

Daniel Mansson, clinical psychologist and co-founder of Flow, said that the company is “increasing treatment choice and empowering people to self-manage their symptoms at home with an effective, personalised and non-pharmacological alternative.”

He continued, “This has the potential to improve the standard of care, and reduce global healthcare costs. The Khosla Ventures investment will support the next stage of our journey as we cement our position as European leaders of brain stimulation treatment for depression.”

Depression is the leading cause of disability worldwide affecting over 300 million people, so effective, non-pharmacological alternative treatments are in high demand. Meanwhile, in the UK, nearly one in four adults are affected by a mental illness.