The same brain structures that process emotion and memory are at the centre of most mental health disorders. Here is how these structures connects to the disorders.
Post-traumatic stress disorder (PTSD) occurs when the brain’s danger detection system remains on high alert long after a threatening event has passed. These traumatic experiences cause physiological changes in the brain. First responders, such as police officers, are particularly prone to exposure to trauma and therefore face a higher risk of developing PTSD.
The amygdala in individuals with PTSD becomes overactive, a condition that arises immediately following the traumatic event. When exposed to triggers that merely resemble the original trauma—such as similar smells, sounds, or locations—it sends out alarm signals. At the same time, the hippocampus may shrink, making it difficult for the brain to accurately place memories within their temporal context. Multiple studies have also found that exposure to violence and trauma leads to a reduction in the volume of the prefrontal cortex (PFC), which helps regulate the emotional responses triggered by the amygdala. When the parts of the brain responsible for thinking and memory fail to function properly, patients find it difficult to distinguish between safe events occurring in the present and dangerous events that occurred in the past. The brain treats current events as past traumatic events, making it difficult for patients to think rationally at that moment. One of the common symptoms of PTSD is flashbacks—involuntary, intense, and often distressing memories of traumatic events triggered by external stimuli. Simply put, patients may experience vivid and disturbing memories that feel as though they are happening again in the present, which can trigger intense emotional and physiological reactions, such as a racing heart and difficulty breathing.
Patients who have not received treatment find it difficult to control their symptoms during flashbacks because, for them, the trauma has never truly passed. With every flashback, they are pulled back to that devastating moment and forced to relive the fear and helplessness they felt at the time.
When the brain’s threat response system becomes overly sensitive—sending alarm signals in situations that are not actually dangerous—it can trigger anxiety disorders.
An overactive amygdala readily sends threat signals. Subsequently, the hypothalamus responds to the perceived stress by releasing cortisol and adrenaline, even when the patient’s surroundings do not actually pose a threat. The prefrontal cortex, which should calm the amygdala through rational thought, struggles to suppress this reaction. As a result, the amygdala overrides the prefrontal cortex, and the patient’s behavior may become inconsistent with their usual personality.
Research shows that prolonged anxiety can lead to enlargement of the amygdala, causing patients to react more intensely to threatening stimuli while also negatively impacting the functioning of the hippocampus and prefrontal cortex.
Depression is not simply sadness. It is a condition in which the brain's ability to feel reward, maintain motivation, and regulate emotion becomes significantly disrupted.
The prefrontal cortex shows reduced activity, making it harder to plan, concentrate, or feel pleasure. The hippocampus can physically shrink if people stay depression mood for a long time, when that part shrink, it might impairing memory. The amygdala may become overactive, amplifying negative emotions. The reward circuits (partly the basal ganglia) stop responding normally to things that used to feel good, means the patients can have difficulties of feeling happiness.
Scientists are still working to determine whether the damage caused by depression to the brain is permanent. Persistent depression is likely to lead to long-term changes in the brain, particularly in the hippocampus. This may explain why depression is difficult to treat in some people. However, researchers have also found that individuals diagnosed with lifelong major depression who have not experienced an episode for many years also have reduced gray matter volume in their brains. Nevertheless, people have already have some methods to halt or even reverse some of these brain changes.
One of the methods is antidepressant medication. These drugs act on the brain’s chemicals that regulate stress and mood. Evidence shows that these medications can help the brain form new connections. The second is cognitive behavioral therapy (CBT). Experts believe that CBT can promote neuroplasticity. This means that through practice, patients can change their brains, thereby helping to alleviate symptoms of depression.
You may have heard that ADHD is caused by laziness or a lack of willpower. However, scientific research shows that the brains of people with ADHD have difference from those people without ADHD in both structure and the way of its working, which may be one of the potential causes. But ADHD is not a lack of attention; people with ADHD can focusing intensely on things that truly interest them. It is a disorder involving difficulties with attention regulation and impulse control.
In people with ADHD, the prefrontal cortex may develop several years later than in their peers and exhibit lower levels of activity. This affects executive functions, including planning, impulse control, and shifting attention. The basal ganglia, which help control movement and filter out distractions, work differently in people with ADHD. This makes dopamine signals less stable and less effective.
That’s why ADHD medications often target dopamine. They help it stay in the brain longer and sometimes increase its release, allowing the brain to regulate attention more consistently and making focus easier to maintain.
Schizophrenia affects the way the brain processes sensory information and distinguishes between internal thoughts and external reality. One of its most well-known symptoms is hallucinations, especially auditory ones, means that the patients may hear the voices that others cannot. Scientists have found that people with this condition may be more prone to genetic defects that disrupt brain development. Additionally, certain chemicals in the brains of people with schizophrenia that control thought, behavior, and emotion are either overactive or underactive. For example, areas of the brain that rely on dopamine may be overactive in people with schizophrenia.
Several brain regions are affected by schizophrenia. The thalamus, it normally filters sensory information before it reaches the cerebral cortex, but schizophrenia patients ‘thalamus may allow too much irrelevant information through and cause the brain overwhelmed. It may also shrink over time.
The temporal lobe, responsible for processing sound, may produce internal signals that are misinterpreted as external voices. At the same time, reduced activity in the frontal lobe can impair reasoning, decision-making, and emotional regulation. As the condition progresses, these changes may lead to more severe symptoms. The temporal lobe, responsible for processing auditory information, may generate internal signals that the brain misinterprets as external sounds. At the same time, reduced activity in the frontal lobe can impair reasoning, decision-making, and emotional regulation. As the condition progresses, these changes may lead to more serious symptoms.
In people with schizophrenia, the hippocampus typically atrophies. Thinning of the cerebral cortex can be observed in multiple brain regions, most notably in the frontal and temporal lobes.
It is one of the most extensively studied conditions in neuroimaging research.
Alzheimer’s disease is not a normal part of aging. It is a condition in which abnormal proteins accumulate in the brain, gradually causing brain cells to die. Initially, this process is confined to specific areas, but it gradually spreads over time.
Alzheimer's disease is not a normal part of aging. It is a disease caused by the accumulation of abnormal proteins in the brain, which gradually leads to the death of brain cells. Initially, this process is confined to specific areas of the brain, but it gradually spreads over time.
In the early stages of Alzheimer’s disease, the neural connections in the memory-related parts of the brain—such as the hippocampus—are typically damaged. This is why people with early-stage Alzheimer’s often have difficulty forming new memories, while old memories may persist for a long time. As the disease progresses, the amygdala shrinks, leading to emotional changes. Various regions of the cerebral cortex gradually deteriorate, ultimately affecting language skills, reasoning abilities, and personality traits. In the late stages of the disease, brain damage becomes so widespread that patients lose the ability to communicate and require care from others.
The pathological progression of this disease corresponds directly to the structure of the brain.