There are millions of reasons why … actually, millions of humans.

So why might these bugs make us feel more bummed?

These bacteria might affect levels of certain neurotransmitters that have been proven to be related to depression, likeglutamate.

an illustration of a silhouette of a person with an illustration of bacteria in a gut overlaid

Images: Getty Images; Collage: Cassie Basford

The microbiome produces neurotransmitters such asNANA,serotoninandnorepinephrine, and billions of good gut bacteria help make that possible.

), and up the optimism ante by stocking up on12 fiber-rich foods to help with good gut bacteria.

Keep in mind that no food or diet will prevent or cure depression.

A multifaceted treatment plan including mental health counseling, medication and lifestyle adjustments is often the preferred approach.