(Nature) – Worldwide, around one-quarter of adults feel very or fairly lonely, according to a 2023 poll conducted by the social-media firm Meta, the polling company Gallup and a group of academic advisers. That same year, the World Health Organization launched a campaign to address loneliness, which it called a “pressing health threat”.

But why does feeling alone lead to poor health? Over the past few years, scientists have begun to reveal the neural mechanisms that cause the human body to unravel when social needs go unmet. The field “seems to be expanding quite significantly”, says cognitive neuroscientist Nathan Spreng at McGill University in Montreal, Canada. And although the picture is far from complete, early results suggest that loneliness might alter many aspects of the brain, from its volume to the connections between neurons. (Read More)