You can’t see them, taste them, or feel them, but they are inside of you right now. Microplastics are pieces of plastic that are smaller than 5 millimeters—about the size of a sesame seed—and they have infiltrated virtually every system in the human body. Researchers have found them in human blood, lungs, liver, placenta, breast milk, and the brain. While much of the public discussion has focused on how they increase our risk of cancer and cardiovascular disease, research now suggests that microplastics may be affecting our mental health.
A 2024 study published in the New England Journal of Medicine looked at arterial plaques (blockages in arteries) from 304 patients and found microplastics in the majority of samples. Individuals with plaques had higher rates of heart attack, stroke, and death. In 2025, a review described the presence of polystyrene microplastics in mouse brains, confirming that the particles can penetrate the blood-brain barrier.
Plastics Affect Our Hormones
One of the most well-documented mechanisms of microplastic toxicity is endocrine disruption. Plastics contain and absorb a range of chemicals that mimic or block estrogen, testosterone, thyroid hormones, and cortisol. A 2025 review found that micro- and nanoplastics disrupt the primary systems that control reproductive function, metabolism, sleep, stress response, and mood.
The hypothalamic-pituitary-adrenal (HPA) axis, which coordinates our response to stress, is particularly vulnerable. Experimental animal studies summarized in a 2025 review suggest that microplastics can disrupt neurotransmitter systems, including catecholamines, thereby impairing their ability to mount an effective stress response. Chronic disruption of cortisol regulation and reduced catecholamines can contribute to anxiety and depression. Similarly, disruption of thyroid hormones, which occurs following exposure to microplastics, is linked to depression, cognitive slowing, and fatigue.
Bisphenol A (BPA) exposure is particularly important. Prenatal BPA levels have been associated with later behavior problems in children, including increased anxiety, depression, and impaired social development. A 2023 review confirmed that nanoplastics disrupt brain signaling that regulates hunger and sleep, both of which influence mental illness.
Rewiring Neurotransmitter Systems
In addition to disrupting hormones, microplastics directly affect the brain. They can induce neurotoxicity by contributing to oxidative stress and neuroinflammation. Microplastics can disrupt neurotransmission resulting in altered behavior and cognitive impairment. They can also alter our neurochemistry. A 2025 review of animal studies showed that microplastic exposure disrupts dopamine, serotonin, glutamate, and GABA signaling. Polystyrene nanoplastics can deplete dopamine, which is associated with anhedonia, lack of motivation, and depression. Reduced serotonin is a marker for anxiety and depression.
In mouse models, depressive-like behaviors have been induced by exposure to nanoplastics, with studies reporting impaired motor activity, disrupted social behavior, and autism spectrum disorder-like changes. The changes appear to be caused by neuroinflammation that triggers oxidative stress, synaptic dysfunction, and impaired removal of damaged neurons.
The Gut-Brain Axis: A Hidden Pathway
The gut microbiome is made up of trillions of microorganisms in our stomach and intestines. This collection of bacteria, viruses, and fungi significantly influences our brain chemistry and behavior, representing another pathway through which microplastics can influence mental health. A 2024 study found that microplastic exposure promotes dysbiosis, a disruption of the normal balance of organisms in the gut. Microplastics also reduce microbial diversity and cause leaky gut.
A 2024 review titled “Mind over Microplastics” concluded that disruption of the gut caused by microplastics may cause psychiatric symptoms via the gut-brain axis,. The authors noted that the particles pass from the gut into the immune system and, later, into the nervous system.
What Can We Do About It?
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While it’s impossible to completely avoid plastics, you can reduce your exposure and lessen the harm caused by plastics.
Filter your water. Tap water is one of the primary sources of microplastics. High-quality reverse osmosis or activated carbon filters significantly reduce microplastics. Avoid single-use plastic bottles, which also leach microplastics, particularly when they are exposed to heat.
Rethink how you store and prepare your food. Heat dramatically accelerates the leaching of plastics into food and beverages. Use glass, stainless steel, or ceramic containers, especially for hot liquids. Never microwave food in plastic containers, and avoid using plastic cutting boards because microplastics are released every time you make a cut with a knife.
Prioritize dietary fiber and gut health. A 2024 review found that dietary fibers bind to microplastics in the GI tract and promote their excretion while, at the same time, restoring the integrity of the gut barrier. Probiotic and prebiotic foods support microbiome diversity in the gut, thereby buffering against inflammation.
Increase your intake of antioxidants. Polyphenols found in green tea, berries, and dark chocolate have been shown to help counteract the oxidative stress produced by microplastics. Omega-3 fatty acids, which are found in fatty fish, flax seeds, and walnuts, reduce neuroinflammation and improve cellular membrane integrity.
Reduce your indoor air exposure to plastics. Synthetic textiles, carpeting, and household dust are major sources of airborne microplastics. Ventilating living spaces, using HEPA air filters, and choosing natural fiber furnishings and clothing can reduce the inhalation of microplastics. Inhaled microplastics can impair immune system functioning and cause neurotoxicity.
Another approach is to advocate for change. Demand limits on production of plastics, stricter regulation of endocrine-disrupting additives, and mandatory microplastic testing of drinking water. Mental health practitioners can raise awareness of environmental factors that contribute to mental illness.
A New Frontier in Mental Health
The science linking microplastics to mental health remains in its early stages, and much of the evidence comes from animal models. Direct evidence in humans is still accumulating. But the plausibility is substantial. Research in animals has found that microplastics can cross the blood-brain barrier and damage neurons in the brain, disrupt hormones that regulate mood, alter neurotransmitter systems, and degrade the gut microbiome in ways that increase inflammation and increase the risk of psychiatric disorders.
As mental health professionals, we are trained to look for biological, psychological, and social contributors to mental illness. It is time to add a fourth dimension—environmental. The air we breathe, the water we drink, and the containers we heat our food in may be contributing to the global mental health crisis. Reducing exposure to plastics isn’t just important for our patients. It’s important for each and every one of us.