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“If you’re going through hell, keep going.” –Winston Churchill
Shockingly, suicide is the second leading cause of death for people between the ages of 18 and 29 years. For friends and family, it is heartbreaking.
These days, we’re highly connected yet lonely, our jobs are being stolen by artificial intelligence (AI) and robots, climate change is clouding our future, and pandemics are no longer theoretical. Stressors abound. But there is another factor hidden inside our bodies that may also be a threat to our mental state: microbes.
An exploratory study in 2021 from the Baylor College of Medicine in Houston found little correlation between suicide and gut microbes, but it wasn’t the last word. In the intervening years, new studies have found important new connections.
Oral microbes
A recent Chinese study found a link between oral microbes and suicidal tendencies in high school students. They compared 45 healthy controls to 45 kids with suicidal ideation and found a microbial connection.
In particular, they found Enterobacter, Escherichia, Shigella, and Parabacteroides in the oral microbiome of the suicidal kids. In contrast, the healthy controls had higher levels of Rikenellaceae and Alistipes.
Microbiomes are an ecosystem writ small, and like any good ecology, diversity is the key to resilience. If rabbits are the only food available for the bobcats, then when rabbits die out, the bobcats will soon follow. But if there are multiple prey animals, the bobcats have much better odds of survival.
Sure enough, the microbial diversity of suicidal kids was significantly lower than that of the control group. That is destabilizing and provides many opportunities for die-offs of beneficial microbes. This unbalanced state is called dysbiosis, and it is a key signature of suicidal tendencies.
This establishes an association but doesn’t directly show causation. Although the dysbiosis is likely instrumental, the gut-brain axis is a two-way street: Microbes affect the brain, but the brain can also impact microbes.
From a strict reading of the science, that is less than satisfying, but loops like this are common in biology. Does it even matter? The bidirectional traffic actually gives us two possible ways to intervene. We might improve our microbiome with diet, or we might improve our mood with therapy. Since we can alter either side of the loop, we can effectively double the possible interventions. Either way may allow us to convert a vicious cycle into a virtuous one.
Gut microbes
Another study, this one from Iran, found a link between suicide and the gut microbiome. As in the oral study, they found a reduction in microbial diversity among the suicidal subjects.
They found specific microbes associated with suicidal thoughts, namely Fusicatenibacter, Hungatella, Veillonella, and Megasphaera. They also found microbes associated with mental health, including Clostridium, Butyricicoccus, Desulfovibrio piger, and Parabacteroides merdae.
It is worth noting that these healthy bacteria are involved in the production of short-chain fatty acids like butyrate that are like ambrosia to the cells lining the gut, simultaneously healing and nourishing them. Butyrate is an amazingly potent substance that can travel to the brain, where it encourages the growth of new nerve cells, improving memory, cognition, and mood.
The researchers tested the so-called “leaky gut” hypothesis that describes how tiny ruptures in the intestinal wall can allow toxins and even microbes to enter the bloodstream. The Iranian researchers found evidence of gut breakdown in patients who had attempted suicide. When the gut gets leaky, the immune system kicks into action, chasing down the intruders as the heart blithely pumps them to every organ in our body, including the brain.
The brain has a barrier intended to keep microbes and immune cells out, because both can kill cells. While most of our organs can regenerate tissue to some extent, the brain is special. When nerve cells die, so do memories.
The brain senses inflammation and responds with anxiety. This is an appropriate reaction honed by evolution to encourage us to withdraw and avoid social contact, preventing the spread of disease.
Chronic inflammation
If the cause is just a bad bite of sushi, gut leakage should resolve quickly, and we can bounce back. But if the insult is continuous, say from a funky diet or an overbearing boss, then something different happens. The stress becomes chronic, which can weaken the brain’s barrier, and the immune battle can spill over into the brain itself. That can lead to major brain dysfunction, including psychosis.
Indeed, the Iranian researchers noted that an important inflammatory molecule, interleukin-6, was elevated in the cerebrospinal fluid of people who attempted suicide. Intriguingly, the association was even stronger among those who chose more violent methods.
Some 90 percent of suicides occur in people with pre-existing mental disorders, and the researchers looked at how the gut-brain axis affects specific psychiatric conditions. They found that anti-inflammatory bacteria like Faecalibacterium were reduced in people with depression. They also found bacterial shifts in people with psychosis and schizophrenia. These findings echo previous studies of the gut-brain axis.
The researchers point out that suicidal ideation is multifactorial. There are genetic components and environmental insults that contribute. But we have no control over our genes, and a big part of anxiety and depression is due to a lack of control over a malignant environment.
But we can change our microbes.
What to do
Although these studies don’t demonstrate causality, it is not crazy to think that improving your microbiome could improve your mood and reduce thoughts of self-harm. The microbes that improve mood are called psychobiotics.
We know what they like: plenty of fiber (from veggies) and ferments (like kraut, kimchi, and yogurt). This is part of the Mediterranean diet that purports to deliver a long and happy life. We also know that alcohol and opioids can exacerbate a leaky gut.
It may not relieve all the stress in our lives, but improving our microbiome is practically cost-free and enormously helpful. As this research implies, it may even save lives.
If you or someone you love is contemplating suicide, seek help immediately. For help 24/7 dial 988 for the 988 Suicide & Crisis Lifeline, or reach out to the Crisis Text Line by texting TALK to 741741. To find a therapist near you, visit the Psychology Today Therapy Directory.
