A Chinese research team has found for the first time that social isolation triggers iron accumulation in specific brain regions involved in emotional regulation, which in turn increases social anxiety.

The findings, published in late January in the international journal Cell Metabolism, identify iron as a key indicator of social isolation-induced anxiety. Researchers say the discovery helps explain how loneliness harms the brain and points to a potential noninvasive, reversible intervention independent of traditional anti-anxiety medications.

The study was led by Wang Zhuo, an associate professor at South China University of Technology's School of Medicine, in collaboration with Zhejiang University and Southern Medical University in Guangzhou, Guangdong province.

Iron has long been regarded as a nutrient essential for neural health. However, the study found that under psychological stress, iron can act as a double-edged sword, directly driving structural and functional remodeling of neural synapses, Wang said.

The team established a mouse model simulating long-term solitary living conditions in humans and found that individually housed mice had abnormally elevated iron levels in the ventral hippocampus, a subregion primarily responsible for emotional regulation.

"Notably, this iron accumulation is by no means beneficial; excessive iron acts as an erroneous signal to activate alpha-synuclein, thereby inducing abnormal neuronal hyperexcitability," Wang said.

He compared the process to an electrical short circuit, saying it persistently transmits anxiety-related signals of danger and escape throughout the body.

"More critically, such alterations specifically target the emotional center, endowing the brain with a highly specific stress response to social deprivation," Wang said.

The team named the newly identified mechanism "ferroplasticity", defined as iron-mediated, experience-dependent neuroplasticity. The researchers said the mechanism directly links cerebral iron metabolism disorders to affective disorders and opens a new window for understanding the metabolic origins of psychiatric diseases.

"In the future, people with anxiety disorders may bid farewell to drug dependence," Wang said.

In experiments, the team targeted key molecules involved in ferroplasticity — iron or alpha-synuclein — through nasal administration. Within two weeks, anxiety behaviors in the mice decreased significantly and neuronal activity returned to normal. The effects appeared faster than reintegrating the mice into group living, or "resocialization", which requires four weeks.

"This implies that a nasal spray may suffice to safely and conveniently prevent or alleviate anxiety in high-risk groups such as elderly people living alone, workers in isolated posts, post-operation isolated patients and adolescents with social avoidance in the following years," Wang said.

Wang said more than one billion people worldwide who are affected by social isolation-related psychological problems could potentially benefit from the findings, which he described as providing a new paradigm for developing noninvasive, precisely targeted anti-anxiety therapies.

The team plans to advance research on human safety and dosage optimization of the nasal spray formulations, develop noninvasive imaging techniques to detect ventral hippocampal iron deposition, and explore whether the mechanism plays a role in other neuropsychiatric disorders.

"We will strive to initiate clinical trials soon to truly translate the scientific findings into benefits for the public," Wang said.

According to Wang, the World Health Organization has listed social isolation as a major global health threat, one that has become increasingly prevalent in the 21st century.