Why the bacteria in your intestines could be making you depressed

    29 July 2015

    The bacteria in your intestines could be inducing anxiety and depression, according to new research carried out by scientists at McMaster University, Ontario. Although it has long been known that intestinal bacteria affects behaviour, this is the first study to investigate altered behaviour as a consequence of early life stress.

    The researchers subjected mice to early life stress by removing infants from their mothers for several hours at a time. Premysl Bercik, the paper’s senior author, explains what they discovered by doing so:

    ‘We have shown for the first time in an established mouse model of anxiety and depression that bacteria play a crucial role in inducing this abnormal behaviour. But it’s not only bacteria, it’s the altered bi-directional communication between the stressed host – mice subjected to early life stress – and its microbiota, that leads to anxiety and depression.’

    When the experiment was repeated in a germ-free environment, mice that were maternally separated had altered stress hormone levels and gut dysfunction, but didn’t show any signs of anxiety or depression.

    ‘Our data show that relatively minor changes in microbiota profiles or its metabolic activity induced by neonatal stress can have profound effects on host behaviour in adulthood.’

    This research demonstrates that early life stress can lead to the development of bacteria that induces depression and anxiety – in mice, at least. For obvious reasons it wouldn’t be possible to repeat the experiment on humans, but the researchers believe that by examining the intestinal bacteria of people who already suffer with depression, they can establish whether or not it affects humans in the same way.

    Combined with research that shows that a low income can damage children’s brains, this isn’t good news for people who didn’t get the best start in life.