For many years, conditions such as depression and anxiety were viewed primarily through a psychological lens.
Modern neuroscience is revealing a deeper biological picture.
The brain, like the rest of the body, has its own immune system. When functioning normally this system protects delicate neural tissue from infection and injury. However, when inflammatory signalling becomes chronic, it can disrupt how brain cells communicate.
This process is known as neuroinflammation.
Neuroinflammation occurs when immune cells in the brain become overactive and release inflammatory molecules that alter neurotransmitter balance, neural communication and cellular energy production.
Researchers are now investigating how this process may contribute to depression, anxiety, brain fog and neurodegenerative disease.
The brain’s immune cells
The brain contains specialised immune cells called microglia.
Microglia act as the brain’s surveillance system. They monitor the environment, remove damaged cells and respond to infection or injury.
When activated briefly they are protective. However, chronic stress, metabolic imbalance, persistent inflammation in the body and environmental stressors can keep these cells activated for long periods.
When this happens inflammatory signals can interfere with normal brain signalling, influencing mood, cognition and motivation.
The inflammation and mood connection
A growing body of research suggests that inflammation can influence mood by affecting neurotransmitters involved in emotional regulation.
Inflammatory signalling may alter the function of serotonin, dopamine and glutamate, which are key chemicals involved in motivation, mood and cognitive function.
Inflammation can also affect the body’s stress response system known as the HPA axis, influencing how the brain responds to physical and emotional stress.
This emerging understanding is helping researchers explain why depression is often seen alongside conditions involving chronic inflammation such as autoimmune disorders, metabolic disease and long term stress.
A shift toward brain circuit research
Another major development in neuroscience is the growing study of brain circuit dysfunction in depression.
Using advanced brain imaging techniques, researchers are beginning to identify specific neural networks that behave differently in people experiencing depressive symptoms.
Rather than being one single disorder, depression may represent several different biological patterns affecting circuits responsible for emotional regulation, motivation, cognitive control and stress response.
Recent research using functional MRI and machine learning has identified distinct biological “biotypes” of depression based on patterns of activity across these neural circuits.
Importantly, these patterns appear to influence how individuals respond to treatment.
This may help explain why some people respond well to certain medications while others experience little benefit from the same approach.
As neuroscience advances, identifying these neural patterns may allow clinicians to tailor treatments more precisely to the underlying biological drivers involved.
Where neuroscience is heading
Advances in brain imaging and functional neurosurgery are helping scientists map the neural circuits involved in mood regulation.
Researchers studying the brain’s connectome are beginning to identify networks that regulate emotion, motivation and cognitive control. In some individuals these circuits appear underactive, while in others certain regions become overactive.
Understanding these patterns is opening the door to more targeted approaches to treatment.
In recent years neurosurgeons and neuroscientists have begun exploring therapies designed to influence specific brain circuits. Techniques such as deep brain stimulation and transcranial magnetic stimulation aim to regulate activity in neural networks involved in mood regulation.
This emerging field suggests that depression may involve dysfunction within particular brain circuits rather than a single chemical imbalance.
Identifying these circuit patterns may eventually allow clinicians to tailor treatments more precisely, matching therapies to the underlying biological drivers involved.
A key brain region in depression research
One brain region that has attracted significant attention in depression research is the subgenual anterior cingulate cortex, sometimes referred to as Area 25.
This region sits deep within the brain and acts as a communication hub between emotional processing centres and areas responsible for decision making and cognitive control.
Brain imaging studies have shown that this region can become overactive in individuals experiencing severe or treatment resistant depression.
Researchers have found that when activity within this circuit is regulated, depressive symptoms may improve. These findings have led to treatments designed to influence specific neural networks involved in mood regulation.
This research highlights an important shift in how scientists understand depression. Rather than being a single disorder, depression may involve dysfunction within particular brain circuits that regulate emotion, motivation and stress response.
The role of plant compounds
While research into brain circuits continues to evolve, scientists are also studying how plant compounds influence inflammatory pathways and cellular protection within the brain.
Many herbs traditionally used in herbal medicine contain polyphenols and bioactive molecules that support antioxidant defence and modulate inflammatory signalling.
For example:
Turmeric (Curcuma longa) contains curcumin, a compound studied for its ability to regulate inflammatory pathways and support neuronal protection.
Ashwagandha (Withania somnifera) contains withanolides that support stress regulation and have demonstrated neuroprotective properties in research.
Rosemary (Rosmarinus officinalis) contains compounds such as carnosic acid and rosmarinic acid which support antioxidant defence in neural tissue.
These plants demonstrate how herbal medicine often works by supporting the biological environment in which healthy brain signalling occurs rather than simply targeting symptoms alone.
A systems perspective
The brain does not function in isolation.
Inflammation within the brain is influenced by signals from the immune system, the gut microbiome, metabolic health and chronic stress.
Understanding these interconnected systems is helping reshape how we think about mental wellbeing.
As neuroscience continues to evolve, the relationship between inflammation, brain circuits and cellular resilience is becoming one of the most important frontiers in modern medicine.
Research
Inflammation and depression research
https://pubmed.ncbi.nlm.nih.gov/26892344/
Brain circuit biotypes of depression
https://www.nature.com/articles/s41591-024-03057-9
Subgenual cingulate and depression research
https://pubmed.ncbi.nlm.nih.gov/19923284/
Curcumin and neuroinflammation
https://pubmed.ncbi.nlm.nih.gov/19303921/
Â