http://www.nature.com/mp/journal/vaop/ncurrent/full/mp201650a.html

From gut dysbiosis to altered brain function and mental illness: mechanisms and pathways

For example, a link between Antibiotic exposure and altered brain function is well evidenced by the psychiatric side-effects of Antibiotics , which range from anxiety and panic to major depression, psychosis and delirium.1

A recent large population study reported that treatment with a single Antibiotic course was associated with an increased risk for Depression and anxiety, rising with multiple exposures. 27

Bercik et al.28 showed that oral administration of non-absorbable antimicrobials transiently altered the composition of the gut microbiota in adult mice and increased exploratory behaviour and hippocampal expression of brain-derived neurotrophic factor (BDNF), while intraperitoneal administration had no effect on behaviour.

Alteration of brain function may therefore add to the many reasons that inappropriate Antibiotic use should be avoided.

It should be noted though that unchecked bacterial infection also represents an acute stressor, and has been shown to be associated with memory dysfunction in mice. 29