Getting an infection is no fun. Sometimes it’s necessary to take an antibiotic in order to prevent the infection from causing serious damage.
However, antibiotics are becoming less effective these days due to over-prescribing them and causing resistant bacteria. Sometimes we really don’t need to take them and they may be doing more harm than good.
There are definitely physical side effects to consider before unquestioningly taking this medication. You could experience nausea, vomiting, stomach cramps, diarrhea, loss of appetite, bloating, and indigestion.
I personally have experienced nausea, fatigue, headaches, and some nasty body aches from a course of antibiotics. These side effects should be expected since the root of the word “anti-biotics” comes from the Greek meaning “kill-life.”
When you take broad-spectrum antibiotics – meaning they kill all bacteria indiscriminatly – (and most antibiotics are broad-spectrum), they inevitably have an effect on the delicate balance of your gut microbiome. Instead of just killing the bad, pathogenic bacteria, they also kill the beneficial bacteria that we need to stay healthy. So of course, it should come as no surprise that our physical health may be impacted by taking them.
But what about mental side effects?
Can antibiotics cause depression? And if so, how does it happen?
How Antibiotics Can Cause Depression
There was a nested case-control study done using medical records of hundreds of thousands of people in the United Kingdom during 1995-2013 that proved antibiotic use increases the risk of depression and anxiety. They saw this even in cases of just one course of antibiotics, although with multiple courses the risk goes up.
This happens because antibiotics disrupt your gut microbiome.
Your gut microbiome is the bacteria, fungi, viruses, and yeasts that cover your gastrointestinal tract from the mouth all the way through to the rectum. These bacteria help digest food, support the immune system, balance our hormones, and create neurotransmitters that communicate directly with the brain.
So killing our gut bacteria will surely have an effect on our mental health as the gut microbiome creates the neurotransmitters that influence our emotional state of being.
Our gut produces 90-95% of our “happy hormone,” serotonin, and 50% of our “pleasure chemical,” dopamine. It also produces GABA which helps us feel calm and relaxed. One example of antibiotics changing our emotional state is that certain very common antibiotics such as penicillin, have structures that mimic GABA and could potentially block the GABA receptors, causing anxiety.
So not only can they block our neurotransmitters, antibiotics directly kill the bacteria that produce these chemicals necessary for mental health.
It’s very clear that antibiotics can trigger depression.
Antibiotics Let In Pathogens
The gut microbiome also helps to digest our food and process vitamins from that food, but it also produces vitamins. Without that function, we don’t have the necessary building blocks for physical or mental health. For example, B vitamins have a positive effect on mood and are produced by certain gut bacteria. Omega-3s and vitamin D also boost mood and we need to make sure that these are being properly absorbed.
Our gut is also very intimately tied to our immune system.
The gut contains about 70% of the body’s immune cells mostly located in the gut-associated lymphoid tissue (GALT) in the intestines. Most people don’t realize that we have lymph nodes in the gut.
Lymph nodes filter our lymphatic fluid which contains white blood cells, or lymphocytes. Our white blood cells are the key players in your immune system that fight off pathogens and infection.
Our bacteria actually train our white blood cells. I talk more about how the gut microbiome and immune system are connected in another article.
So when our good bacteria are no longer working along with our immune system, we are down a line of defense and are more likely to get sick. Getting sick means we have inflammation. If we are always getting infections, we have chronic inflammation.
Chronic inflammation can cause depression.
We are also more likely to be invaded by bacteria that cause depression.
Bacteria Can Cause Depression?
Researchers are finding that certain pathogenic bacteria may contribute to or cause depression. There is still a lot to be discovered in this area of study but so far there are several bacteria they are looking into including Clostridium, Alistipes, E. coli, Shigella, Salmonella, Bibrai, Campylobacter, Yersinia enterocolitica, Aeromonas, and Listeria. 
If scientists can find a way to target only the pathogenic bacteria that is causing depression or any infection for that matter, then there would be no harm done to all the beneficial bacteria responsible for keeping us healthy.
Antibiotics Cure Depression?
Believe it or not, a broad-spectrum antibiotic called iproniazid started being used as an antidepressant back in 1951 when doctors noticed that a side effect of taking the drug was happiness. They only paid attention to the fact that it increased serotonin in the brain and it leads to the creation of several antidepressants we all know today, like Prozac.
While they were focused on just the neurotransmitters, they forgot the obvious fact that iproniazid must have killed bacteria that were somehow slowed our serotonin production, or inhibited the reception of it. So we were never able to get to the root of the problem. 
Today they are trying to come up with some more effective narrow-spectrum antibiotics that actually target the specific bacteria that is causing the infection without damage to your gut microbiome.
It’s clear that there are several ways antibiotics interfere with mood and cause depression.
If you are ever in need of antibiotics ask your doctor if there is a narrow-spectrum antibiotic available for your infection. If not, make sure to repopulate your gut with some good quality probiotics to help restore balance after your treatment.
In the meantime, you may want to try a probiotic that will help restore specific bacteria that can help lift your mood.
Healing is a process. Don’t forget to eat a healthy diet, drink water, get outside in nature for a great natural source of healthy bacteria, meditate, and make time for yourself.
Let us know in the comments your experience with antibiotics and how it’s affected your physical and mental health.
 Anderson, Scott C. (2017) Chapter 7, ‘Your Personal Psychobiotic Journey,’ The Psychobiotic Revolution: Mood, Food, and The New Science of the Gut-Brain Connection, Washington, D.C., National Geographic, 207.
 Anderson, Scott C. (2017) Chapter 6, ‘Discovering Psychobiotics,’ The Psychobiotic Revolution: Mood, Food, and The New Science of the Gut-Brain Connection, Washington, D.C., National Geographic, 150.
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