Last year, a study carried out by Johns Hopkins University reported the damning evidence that, of the patients admitted to hospital with mania, five times more of them had been using antibiotics than not using them.1
In that study was quietly revealed one of medicine's dirtiest little secrets—namely, that antibiotics don't just mess up
your gut, but also severely affect your mental health.
The link between antibiotics and psychiatric illnesses has been known for some time, but is rarely highlighted by the mainstream medical establishment. An article published 20 years ago in the Harvard Review of Psychiatry mentions antibiotics as linked to cases of major depression, panic attacks, delirium and psychosis.2
In some cases, the adverse effects of certain antibiotics on mental health have actually been listed in the drug's insert packaging. For instance, in addition to the many serious physical side-effects listed for the fluoroquinolone antibiotic Levaquin, the insert also mentions the following effects, which can appear after just one dose: "Confusion, hallucinations, paranoia, depression, nightmares, insomnia, and, rarely, suicidal thoughts or acts".3
Another antibiotic, clarithromycin, belonging to the class of macrolide antibiotics, derived from soil-borne bacteria, lists side-effects such as "confusion about identity, place and time"; "feeling of unreality"; "feeling that others are watching you or controlling your behaviour"; "feeling that others can hear your thoughts"; and "feeling, seeing, or hearing things that are not there".4
But such detrimental psychological effects are not just limited to these two classes of antibiotics. When researchers from Harvard, Massachusetts General Hospital and Brigham and Women's Hospital reviewed all the available scientific reports, they found mental issues, like delusions and hallucinations, associated with 54 different antibiotics across 12 different classes of these drugs,5 which included everything from sulphonamides and ciprofloxacin to intravenous penicillin. In 70 per cent of cases, electrical activity in the brain was also abnormal, and nearly half of those studied had delusions or hallucinations.
The fact that antibiotics can interfere with brain function shouldn't come as a surprise. These drugs decimate gut flora, and it is now established that the health of the microbiome, and diversity of bacterial colonies that comprise it, can have an impact on the brain.6
It's also been discovered that certain bacterial species in the gut create mood-altering chemicals. Bacillus bacteria, for example, can make norepinephrine (noradrenaline), a hormone and neurotransmitter that increases anxiety and restlessness, and promotes vigilance. These bacteria can also produce dopamine which, in excess, has been linked to bipolar disorder and, at very low levels, to schizophrenia. This happens because "chemically, gut microbes and the brain actually speak the same language".7
Serotonin is a neurotransmitter that affects mood, sleep, memory and arousal. However, 90 per cent of serotonin is produced by specific cells in the gastrointestinal tract and is only possible due to the actions of various species of friendly spore-forming bacteria,8 which are wiped out by antibiotics.
Gamma-aminobutyric acid (GABA), an amino acid that acts as a neurotransmitter in the brain, inhibits nerve impulses, so preventing anxiety and panic attacks. It's also been shown that good-guy bifidobacteria and lactobacilli probiotics can both produce GABA,9 yet more evidence that the bugs in our gut influence our overall mood.
Recent research has also highlighted the importance of what's known as the gut-brain axis, a two-way communication system between the gut and the central nervous system.10
Gut bacteria are an essential element of this communication pathway, as they help to regulate the hypothalamic-pituitary-adrenal (HPA) axis, considered the core regulator of the body's stress response.11 HPA dysfunction is associated with such conditions as post-traumatic stress disorder (PTSD), depression and borderline personality disorder.12
The hypothalamus is the part of the brain that sends messages to the pituitary and adrenal glands, both of which then release a number of stress-related hormones. The type and number of bacterial colonies can also affect how the HPA functions.
The mechanisms by which all this happens are complex, but according to researchers at Kyushu University in Japan, "There is now overwhelming evidence that . . . components of the bacterial cell wall . . . stimulate immune cells within the gut or elsewhere" to release certain cells that influence the parts of the central nervous system involved in the HPA
To emphasize the importance of gut bacteria in the regulation of the HPA axis and the effects on responses to stress, a study was carried out at the University Cork in Ireland with mice bred to be germ-free (no microorganism exposure whatsoever, including the good bacteria). The results indicated that these mice exhibited HPA hyperactivity in the face of even only minor stressors.14
While animal results may not necessarily apply to humans, a team of Italian psychologists at the University of Florence have shown that humans can also display hypersensitive HPA-related stress responses after early severe childhood trauma and with PTSD.15 One of the major effects of too much stress is a change in gut-brain interactions, leading to a range of gastrointestinal disorders like irritable bowel syndrome (IBS),16—which, of course, is exactly what happens after the use of antibiotics.
And Canadian researchers from McMaster University in Ontario have gone so far as to suggest that the health of the gut microbiota is, either directly or indirectly, a major factor in predicting whether someone experiencing a traumatic event will go on to suffer from PTSD. As they reported, the evidence suggests that "imbalanced gut microbiota in early life may have long-lasting immune and other physiologic effects that make individuals more susceptible to develop PTSD after a traumatic event".17
Another known cause of mental-health disorders is neuroinflammation, which has been linked to classic psychiatric disorders like "major depressive, bipolar, schizophrenia, and obsessive-compulsive disorders".18 Here, too, the balance of gut microbes is important because certain bacteria, including Lactobacillus and Bifidobacterium, inhibit the body's inflammatory response,19 but if colonies of these types of bacteria are significantly reduced by the use of antibiotics, the body's ability to counteract inflammation is greatly reduced.
If gut dysbiosis is the root cause of so many psychiatric disorders, then there is potentially a simple solution: use prebiotics and probiotics to rebalance the gut, a solution that many scientists studying the microbiome are now beginning
The bolder among these scientists are clearly promoting the idea of using prebiotics and probiotics to alleviate the symptoms of mental illness. In a preliminary study of 45 volunteers, psychiatry researchers at the University of Oxford demonstrated that a food supplement containing prebiotic galactooligosaccharides—naturally occurring short-chain galactose sugar molecules—are natural tranquillizers that significantly reduced cortisol,
the hormone related to anxiety and stress, in all participants compared with a placebo.21
In a further study in which strains of Lactobacillus acidophilus, L. casei and Bifidobacterium were given to volunteers with major depressive disorder for eight weeks, the participants all reported a reduction in their symptoms.22
This relatively new area of research into the microbiome is changing our perspective on the role of bacteria in our lives. Instead of seeing bacteria as the enemy to be wiped out at all costs, they are now being viewed by a new generation of scientists as essential for our physical and mental health. By indiscriminately using antibiotics in our efforts to eliminate them, we're not just damaging our digestion, but our mental health as well.
When a patient shows up with depression, anxiety or even psychosis, instead of reaching for a prescription pad, the doctor's first question when history-taking should be whether a course of antibiotics has recently been taken, and the first prescription should be for pre-/probiotics to rectify the problem. And just imagine the savings on the drugs bill for various mental conditions, currently a reported £3 billion for depression and anxiety alone - enough to transform the NHS in the process.
Antibiotics in the womb
Research has now established a link between gut dysbiosis in pregnancy and detrimental neural development in the foetus, with antibiotics as the main culprit causing a "pro-inflammatory maternal state".1 As antibiotics comprise 80 per cent of all medications prescribed to pregnant mothers, this is now of serious concern to numerous scientists. Indeed, Israeli researchers at Galilee Medical Center and Bar-Ilan University have called for more research in this area "to unravel the role of these drugs in human development".2
Autism and a bad gut
Besides various forms of mental illness, recent research has also linked gut dysbiosis to autism.
When researchers at the University of Reading studied the faecal flora of children with autistic spectrum disorders (ASDs), they were found to have higher levels of the pathogenic bacteria Clostridium histolyticum than did non-autistic children.1 Another researcher found that C. tetani, a ubiquitous bacillus that produces a potent neurotoxin, is also more prevalent in autistic children and is linked to antibiotic use.2
The toxin 4-cresol, produced by C. difficile, inhibits an enzyme that converts dopamine to the neurotransmitter norepinephrine (noradrenaline), and the resulting build-up of dopamine leads to neurodegeneration and symptoms of autism.3 Not surprisingly, elevated levels of 4-cresol are found in autistic children. In addition, C. difficile infection is nearly always caused by antibiotics, especially cephalosporins and quinolones.4