Adverse childhood conditions raise the risk of mental health disorders in adulthood, and a new study shows one way it happens. In young mice, early hardship led microglia, the brain’s immune cells, to trim more synapses on stress-sensing neurons. That rewired the stress response and raised the risk of later mental health problems.
Summary: How mental health disorders arise is complex. New studies show that adverse childhood experiences may also raise the risk of mental health disorders, because they can change how a person responds to stress. In the new study, researchers looked at microglial cells in the brain instead of neurons. Microglial cells play a vital role in brain growth. Researchers found that hard early conditions make microglial cells trim more of the links (synapses) between neurons. That changes stress responses. In the end, it raises the risk of mental health disorders in adults.
Most people picture the brain as a set of neurons linked in a certain way, forming a powerful supercomputer. Thinking depends on how these neurons connect through synapses. Those links form circuits, memories and working units.
That is true. But the brain also has non-neuron cells. They play a vital role in brain growth and in keeping the mind sharp for life. So when these cells do not work right, the risk of brain disorders, brain-wasting diseases and even mental health disorders may rise.
These non-neuron cells do not send signals. But they support neurons, feed them key nutrients and protect them from toxins, infection and more. They play a vital role in keeping the brain’s structure. These cells are glial cells. Depending on the species, they make up 35-60% of all brain cells.
Of the glial cells, microglia are the most common in the brain. They play a vital role in brain growth. They are also a key part of the brain’s immune system.
In recent years, researchers have paid close attention to microglia and their role in brain decline and mental health disorders. Many brain changes are hard to explain by looking at neurons alone. And one of the most common brain cells cannot be ignored in brain disorders and mental health problems.
How do adverse childhood experiences affect mental health in adults?
Researchers at the Departments of Anatomy & Neurobiology, Pediatrics, Neurology, and Physiology & Biophysics at the UCI School of Medicine say neuroscience has focused heavily on neurons. It has neglected the role of microglial cells.
But brain scientists now see that not knowing what glial cells do for brain health may be the missing link. These cells do not send signals, but they play a vital role in building and keeping up the brain. Understanding them may help explain many brain disorders and common mental health problems.
Researchers ran a study in mice to learn how early life adversity (ELA) can shape stress responses later in life. One group of mice lived in near-ideal conditions, with enough light, rest and food. Another group was exposed to hard conditions.
The group exposed to ELA had major brain changes. The changes were mostly in stress-sensitive neurons in the hypothalamus that make corticotropin-releasing hormone (CRH). They happened because microglial cells trimmed the synapses.
Researchers showed that in the growing brain, microglial cells play a key role in forming synapses, building the brain and so shaping stress responses. So ELA changes how the brain works and how it responds to stress.
Researchers found the role of microglial cells, the changed stress responses from hard early conditions, and their role in later mental health disorders. But they noted they have not yet found the molecular pathways behind it.
Researchers still need to learn which molecules cause microglia to go wrong. Knowing this is key to finding ways to prevent it, and even remedies such as mental disorder treatments and childhood trauma treatment.
Frequently asked questions
How do adverse childhood experiences affect the brain?
In a UCI School of Medicine study in mice, early life hardship changed the brain’s stress-sensitive neurons in the hypothalamus. These are the ones that make corticotropin-releasing hormone (CRH). The change came from microglia trimming the synapses on those neurons. Microglia help form synapses in the growing brain. So that trimming changed how the brain responds to stress later in life.
Can childhood trauma cause mental health problems in adults?
It raises the risk. Hard childhood experiences can change the stress response. A changed stress response raises the risk of mental health disorders in adults. The study traced this to microglial cells over-trimming synapses during brain growth. Researchers have not yet found the molecules that drive it. That is the next step toward prevention and treatment.
What are microglia?
Microglia are glial cells. These are the non-neuron cells that support neurons, feed them and protect them from toxins and infection. Glial cells make up 35-60% of all brain cells, depending on the species. Microglia are the most common of them. They help build the growing brain and are a key part of the brain’s immune system.
Related reading
Brain Cells That Brake Heroin Relapse · Blood-Brain Barrier and Neurological Disorders · Antianxiety Drugs and Dementia Risk · Drug Addiction Treatment, St. Louis