Unraveling the Complexities of Mental Illness and Brain: Understanding Causes, Effects, and Treatment 

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Mental illness is a complex and often misunderstood topic affecting millions worldwide. It can manifest in various forms and significantly impact a person’s life, making it difficult to cope with day-to-day tasks.

While there is still much to learn about mental illness, researchers and experts have made significant strides in understanding its causes, effects, and treatment.

This article will explore the complexities of mental illness and brain, uncovering the factors contributing to its development, how it affects the brain, and the different types of mental illnesses.

Understanding Mental Illness and Its Causes 

Now and again, there are moments when we might feel a little down. Even if we know better, there are occasions when we make jokes about somebody being insane or completely off their rockers. 

Although we have all had some experience with mental illness, this does not mean we fully understand or grasp what it entails. 

Mental illness can manifest by affecting your thoughts, feelings, and behavior. 

This can make it difficult for the person to cope with day-to-day life. Understandably, this then causes them a great deal of distress.

Mental illness is something that people often don’t talk about. It can be hard to understand why someone might feel down or act differently than usual. 

But it’s important to remember that everyone is different, and we all have different coping methods.

What Causes Mental Illness 

Mental illness has many causes, including social, environmental, physical, and genetic.

As the name implies, the social causes of mental illness can be social. These causes include long-term stress, debt, losing a loved one, or suffering abuse, neglect, or isolation. 

The environment in which someone lives can also lead to poor mental health. Examples include drug or alcohol addiction, trauma following an accident, military service, or witnessing a crime. 

Physical causes can be a head injury after a fall or seizure.  Finally, genetics can also affect poor mental health (1).  

Despite most external causes, except genetics, mental illness is often linked to the brain. 

This is because there are changes in the brains of people with mental illnesses. 

However, it is important to remember that not everyone with changes in their brain chemistry will have a mental illness. And not everyone who has a mental illness will have a change in their brain chemistry. 

It is worth pointing out that not all diseases that affect the brain are mental health diseases. These include dementia, Parkinson’s disease, epilepsy, and multiple sclerosis. 

These diseases can lead to poor mental health as life-changing diagnoses can be difficult for people to deal with (2). 

The Brain and Mental Health

The human brain is an incredibly complex and intricate organ that controls all our thoughts, emotions, and actions. It regulates various bodily functions, such as breathing, heart rate, and digestion. 

Understanding how the brain works are crucial to understanding mental illness’s complexities and its effects on the brain. 

This section will explore how the brain works and how mental illness can affect its functioning. We will also examine the various neurotransmitters responsible for different activities in the brain, as well as the different regions of the brain affected by mental illness. By the end of this section, you will better understand the link between the brain and mental health.

How Does the Brain Work?

 The human brain controls all our thoughts, emotions, and actions. To understand how the brain works, we must first know that it comprises over 100 billion nerve cells known as neurons. These neurons communicate through electrical signals that flow along their elongated structures called axons.

 At the end of each axon are structures called axon terminals, which connect to other neurons at tiny junctions known as synapses. These synapses enable the transfer of information from one neuron to another via chemicals called neurotransmitters. (3

Different neurotransmitters are responsible for various activities in the brain, such as movement, memory, and emotion. Any activity in the brain, from thinking to feeling, involves activating groups of neurons that work together to create patterns of electrical activity.

Understanding how the various parts of the neuron work and interact with each other can help us gain insights into how the brain works and how it is affected by different conditions and experiences.

How Does Mental Illness Affect The Brain & Other Functions?

 Mental illness can affect the brain and other functions in various ways. Mental illnesses affect the health and well-being of individuals by causing alterations in brain function.

Mental disorders are primarily connected to what happens in the brain. The region of the brain affected by mental illness varies depending on the specific disorder, but it generally interferes with the brain’s normal functioning.

For instance, depression is associated with changes in the limbic system, which regulates emotions and mood. Schizophrenia, however, affects the prefrontal cortex and the hippocampus, which are crucial for memory and decision-making processes.

Mental illnesses also affect the levels of natural neurotransmitters in the brain, like dopamine and serotonin(4), that regulate mood, motivation, and pleasure. 

Ultimately, mental illness affects both the physical and emotional state of individuals, bringing about negative consequences for their health and overall quality of life.

The Chemical Imbalance Theory

However, new research now challenges that theory (5). Based on the theory that low serotonin is linked to depression, anti-depressant medication that boosts serotonin levels in the brain has been used for many years (6) and appears to benefit those with depression. 

Some researchers have suggested that this could result from the placebo effect (7). 

Evidence also points to a protein that transports serotonin, called SERT. However, the chemical imbalance theory still holds some weight (8). 

With the chemical imbalance theory, there is too little serotonin but too much cortisol, the stress hormone. 

Effects of Cortisol on the Brain

High levels of cortisol can cause damage to the brain, specifically the hippocampus. The hippocampus is responsible for learning and memory, so damage to this section of the brain can lead to problems remembering things and the inability to learn, concentrate, or make decisions very easily. 

Eventually, it can also lead to dementia (9). Depression also affects the brain by causing some areas to have reduced activity and others to have increased activity (10). 

Different Types of Mental Illness

Mental illness is a broad term encompassing many conditions, each with its own symptoms and characteristics. This section will explore some of the most common mental illnesses, including schizophrenia, depression, anxiety, and bipolar disorder.

Each condition affects the brain and the person differently, with unique symptoms, causes, and treatment options.

Type of Mental IllnessBrain ChangesKey NeurotransmittersTreatment
DepressionChanges in the limbic systemSerotonin, norepinephrine, dopamineMedications that boost serotonin levels
SchizophreniaInsufficient or excessive dopamine, too few or too many receptors, glutamate, and norepinephrineDopamine, glutamate, and norepinephrineMedications that block dopamine receptors
AnxietyChronic presence of cortisol, enlargement of the amygdalaCortisolTherapy and medications to manage anxiety and cortisol levels
Bipolar DisorderDifferences in size and activity of specific brain regions, such as the prefrontal cortex, amygdala, and striatumDopamineMedication, therapy, and lifestyle modifications to manage mood shifts
Common Types of Mental Illness and Associated Brain Changes


Depression is a common mental illness that affects millions of people worldwide. It is characterized by persistent feelings of sadness, hopelessness, and worthlessness. 

Studies have shown that depression is linked to brain chemistry changes, specifically in the limbic system, which regulates emotions and mood. (4)

The Role of the Limbic System in Depression

The limbic system produces and regulates various neurotransmitters, including serotonin, norepinephrine, and dopamine, crucial in regulating mood, motivation, and pleasure. (5)

Depression is often associated with low serotonin levels, so medications that boost serotonin levels in the brain are often prescribed to treat depression. 

The Chemical Imbalance Theory and its Limitations

However, the chemical imbalance theory is now being challenged, as research has shown that other factors, such as inflammation, stress, and genetics, may also play a role in the development of depression. 

Ultimately, depression affects the brain’s functioning and can significantly change the person’s mood, behavior, and thought processes.


Schizophrenia is an extremely distressing mental illness that can cause the sufferer to see things that aren’t there, have garbled speech, and behave inappropriately or unpredictably (11). 

There are several theories as to what changes in the brain cause schizophrenia. 

Role of Dopamine in Schizophrenia

One is that there is insufficient dopamine in the brain. Another is that there is too much dopamine in some areas but not enough in others. 

This causes issues as dopamine is thought to overstimulate neurons. This can lead to aggressive or impulsive behavior.  Another theory is that there are either too many or too few receptors. 

Receptors are effectively the “lock” in neurons, with dopamine being the “key” that activates them (12). 

This is another extremely complex biological process, and although dopamine appears to affect the brain and behavior, the reason for this is not fully understood (13). 

Other Neurotransmitters Involved in Schizophrenia

To complicate matters further, two other brain neurotransmitters play a part in schizophrenia. These are glutamate and norepinephrine (noradrenalin) (14). 

Medication Used to Treat Schizophrenia

Drugs that block the dopamine receptors is one of the ways in which medication is used to control schizophrenia. However, these have distressing side effects, including muscle spasms, rigidity, and tremors (15), all of which are symptoms of Parkinson’s disease and also linked to low dopamine levels in the brain (16). 

Anxiety and the Brain

Anxiety is when a person is oversensitive to situations and is in a near-constant state of worry or fear. Anxiety disorders cause forty percent of doctor visits (17), a concerning statistic. 

Role of Cortisol in Anxiety

The effect of anxiety on the brain is that the stress hormone cortisol is chronically present. As previously mentioned, this can cause brain damage to the hippocampus (9).  Chronically high cortisol levels can also disrupt sleep (18), worsening anxiety (19). 

Enlargement of the Amygdala in Anxiety

Anxiety also causes enlargement of the amygdala, which makes it hypersensitive. The amygdala is part of the limbic system linked to emotions. 

This oversensitivity of the amygdala is why anxious people are constantly fearful and worried. 

It also makes rational thought and feeling positive much more difficult (18). Unfortunately, the amygdala is not working alone to make you anxious. 

Constant communication between an area in the brain’s frontal lobe and the amygdala enforces the feeling of anxiety and fear.

Bipolar Disorder

 Bipolar disorder is a mental health condition characterized by extreme mood, energy, and activity shifts. 

People with bipolar disorder may experience episodes of mania, which can include elevated or irritable mood, racing thoughts, grandiose notions, and impulsivity, as well as episodes of depression, with symptoms such as sadness, low energy, feelings of worthlessness, loss of pleasure in activities.

These episodes can vary in duration and frequency and may be interspersed with periods of stable mood. 

Brain Changes Associated with Bipolar Disorder

The exact cause of the bipolar disorder is not fully understood, but studies have shown that changes in the brain’s chemistry and structure may play a role. 

Brain imaging studies have revealed that people with bipolar disorder have differences in the size and activity of specific brain regions, such as the prefrontal cortex, the amygdala, and the striatum.

These differences can lead to problems with emotional regulation, decision-making, and impulse control

Treatment typically involves a combination of medication, therapy, and lifestyle modifications and may require ongoing adjustments to achieve optimal symptom management. With appropriate care, people with bipolar disorder can achieve stability and lead fulfilling lives. 

The Science Behind Mental Illness and Recovery

 Mental illnesses often stem from genetic predisposition, environmental stressors, and biochemical imbalances in the brain. Recovery from mental illness is not always straightforward and often requires a combination of therapies, medications, and lifestyle changes.

Psychotherapy, cognitive-behavioral therapy, and medication are all effective treatments for mental illness. However, recovery is a journey unique to each individual, and the path to healing may vary.

Medications help regulate the brain’s chemicals that play a role in mental illness symptoms, while psychotherapy focuses on identifying triggers and developing coping skills.

Lifestyle changes like exercise, eating healthy, and practicing mindfulness can also significantly impact recovery. Seeking treatment and adhering to prescribed therapies consistently is key to managing mental illness and achieving recovery. Individuals with mental illness can lead fulfilling, productive lives with the right support and resources. 


In conclusion, mental illness is a complex and multifaceted condition affecting millions worldwide. It can be caused by various factors, including genetics, environment, physical injury, and social factors, and can significantly impact a person’s life. 

While the topic can be overwhelming, it is important to remember that recovery is possible with the right support and resources.

 Treatment for mental illness involves a combination of therapies, medications, and lifestyle changes. By seeking help and adhering to prescribed therapies consistently, individuals with mental illness can lead fulfilling, productive lives. 


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  2. The risk of developing depression when suffering from neurological diseases https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3546419/
  3. Brain Basics: The Life and Death of a Neuron https://www.ninds.nih.gov/health-information/public-education/brain-basics/brain-basics-life-and-death-neuron
  4. What has serotonin to do with depression? https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4471964/
  5. The serotonin theory of depression: a systematic umbrella review of the evidence https://www.nature.com/articles/s41380-022-01661-0
  6. Overview – Selective serotonin reuptake inhibitors (SSRIs) https://www.nhs.uk/mental-health/talking-therapies-medicine-treatments/medicines-and-psychiatry/ssri-antidepressants/overview/
  7. Placebo Effect in the Treatment of Depression and Anxiety https://www.frontiersin.org/articles/10.3389/fpsyt.2019.00407/full
  8. The serotonin theory of depression: a systematic umbrella review of the evidence https://www.nature.com/articles/s41380-022-01661-0 
  9. Effects of brain activity, morning salivary cortisol, and emotion regulation on cognitive impairment in elderly people https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6616250/
  10. Where in the Brain Is Depression? https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3619732/
  11. Schizophrenia https://www.mayoclinic.org/diseases-conditions/schizophrenia/symptoms-causes/syc-20354443#
  12. What Is Dopamine? https://www.verywellhealth.com/dopamine-5086831
  13. Schizophrenia https://www.healthdirect.gov.au/schizophrenia
  14. Dopamine and glutamate in schizophrenia: biology, symptoms and treatment https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6953551/
  15. The Relationship Between Schizophrenia and Dopamine https://www.verywellmind.com/the-relationship-between-schizophrenia-and-dopamine-5219904
  16. Pathogenesis of Parkinson’s Disease: dopamine, vesicles and α-synuclein https://bit.ly/3fqjtKB
  17. 40 per cent of all GP appointments about mental health https://www.mind.org.uk/news-campaigns/news/40-per-cent-of-all-gp-appointments-about-mental-health/
  18. The Neurobiology of Anxiety Disorders: Brain Imaging, Genetics, and Psychoneuroendocrinology https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3684250/
  19. Anxiety and Sleep https://www.sleepfoundation.org/mental-health/anxiety-and-sleep


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