Antibiotics, a cornerstone of modern medicine, are revealed to have an influence beyond fighting infections. A recent study reveals a link between their use and our mental health.
Scientists focused on modifications to the gut microbiota and their repercussions on the nervous system. Their work, conducted on rodents and human volunteers, confirms that disruption of the gut bacteria appears to precede the emergence of anxiety symptoms.
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A link observed in mice and humans
Animal experimentation served as the starting point. A cocktail of antibiotics was first administered to adult mice. Quickly, analysis of their microbiota revealed a marked imbalance, with a notable decrease in certain bacterial groups. Concurrently, researchers measured a significant drop in levels of acetylcholine, a major neurotransmitter, both in the gut and in a key brain region, the hippocampus. But researchers also quickly noted that the mice exhibited behaviors suggestive of anxiety.
The second part of the study confirmed these observations in humans. 55 patients on antibiotics were compared to people not using them. The first group reported more pronounced anxiety symptoms. Their biological samples showed alterations similar to those in the rodents: a depletion of the microbiota and a drop in acetylcholine levels in the blood and stool. These two parameters were statistically correlated with the intensity of anxiety.
This dual approach establishes a strong correlation between exposure to antibiotics, disruption of the gut ecosystem, and the emergence of anxiety disorders. The suspected mechanism directly involves the rupture of a delicate biological balance. The simultaneous reduction of bacteria from the Bacteroides genus and of acetylcholine appears to play a central role in this phenomenon.
Towards a potential therapeutic avenue
Faced with this finding, researchers tested a strategy to counteract these effects. They administered methacholine, a stable derivative of acetylcholine, to mice previously treated with antibiotics. This intervention allowed for a noticeable attenuation of their anxious behaviors. It also reduced the excessive activation of brain immune cells, microglia, observed in the hippocampus.
These results indicate that the drop in acetylcholine constitutes a functional link in the causal chain linking antibiotics and anxiety. The possibility of correcting the deficit in this neurotransmitter opens a concrete perspective. This indicates that the mental consequences of an antibiotic treatment are not necessarily irreversible and could be modulated.
The study thus underscores the necessity for reasoned prescription of these drugs, already promoted to fight antibiotic resistance. It invites us to consider the microbiota as a full-fledged organ, whose health influences that of the brain. This work could ultimately inspire complementary approaches aimed at protecting or restoring intestinal balance during and after antibiotic treatment.