Antibiotics that are strong enough to kill the gut bacteria also stop new brain cells growing.
Scientists have found that brain cell growth in the hippocampus — a region vital for memory — is slowed by prolonged antibiotic use.
The effects can be countered, however, with exercise and probiotics.
Dr Susanne Asu Wolf, a senior study author, said:
“We found prolonged antibiotic treatment might impact brain function.
But probiotics and exercise can balance brain plasticity and should be considered as a real treatment option.”
In the research mice were given enough antibiotics to clear out their intestines of all microbes.
Their memories and brains were then compared with untreated mice.
The researchers found that mice who lost their healthy gut bacteria performed worse on the memory tests.
They also showed deficits in their ability to produce new brain cells.
The adverse effects, though, could be reversed.
Mice who were given probiotics and who exercised recovered both their memory and their ability to create new brain cells.
Dr Wolf said:
“The magnitude of the action of probiotics on Ly6Chi cells, neurogenesis, and cognition impressed me.”
Many studies are now showing the importance of ‘good’ intestinal bacteria for our mental health.
“Bacteria in the intestine can play an important role in causing anxiety and depression, new research concludes.
It helps explain recent research suggesting probiotics can stop sad moods getting worse.
Probiotics may work to help stabilise the bacteria in the gut.
Another recent study also found probiotics may reduce anxiety.”
And antibiotics have also been linked to mental confusion and even delirium in some patients.
The study was published in the journal Cell Reports (Möhle et al., 2016).