Brain and Mental Disorders

Brain and mental disorders afflict 1 in 4 people worldwide. That is 25% of the world population.  When your brain is damaged, it can affect many different things, including your memory, your sensation, and even your personality. Brain disorders include any condition or disability that affects your brain. This includes conditions that are caused by illness, genetics and injury.

We are going to consider the three categories of brain disorders: brain injury, neurodegenerative disease and mental disorders. All three of these categories of brain disorder have a huge impact on someone’s daily life and well-being.

Let’s start with brain injury, its causes and how it affects your brain and behaviour.  A brain injury can happen at birth or may arise later in life from head trauma, like a bang on the head, from illness or from a stroke. Strokes can and do occur at any age. But the risk of having a stroke more than doubles each decade after the age of 55.  

Stroke is the most common cause of acquired brain injury and has already reached epidemic proportions. Over 13 million people will have a stroke this year and around 5.5 million people will sadly die as a result.

A stroke is the brain equivalent of a heart attack – a brain attack! It happens when the blood supply to part of your brain is cut off. Blood carries essential nutrients and oxygen to your brain. Without blood, your brain cells become damaged or destroyed and won’t be able to function.

As we have already learnt, brain cells send messages around your body to enable you to function. The right half of your brain controls the left side of your body and the left side of your brain controls the right side of your body. And each part of your brain has a specific function, like memory, emotion, movement or vision.  

Because your brain controls everything your body does and all aspects of your behaviour, a stroke or head trauma can affect the way your body functions or the way you behave in many different ways.

If a stroke or head trauma damages the part of your brain that controls your right leg, then you may have paralysis, weakness or numbness in that leg. If you have visual problems, the stroke or head trauma will have damaged visual cortex - the area of your brain responsible for your vision. If you experience changes to your personality, the stroke or head trauma will have damaged the frontal lobe - area of the brain responsible for controlling your personality. 

Stroke can cause permanent damage, including paralysis or impairment or temporary loss of function. The extent and location of the damage determines the severity of the stroke, which can range from minimal to life changing.

Let’s move onto a different class of brain disorders that we call neurodegenerative diseases. Neurodegenerative disease is an umbrella term for a range of conditions, including Alzheimer’s, Parkinson’s, and Huntington’s disease, which result in the progressive degeneration and often death of neurons. Neurons are the building blocks of the nervous system and, except in certain parts of the brain (which we will discuss in Module 3), don’t reproduce or replace themselves. So, when they become damaged or die, they cannot be replaced by the body. 

Alzheimer’s is the most common form of neurodegenerative disease. It is an irreversible, progressive brain disorder that slowly destroys memory and thinking skills and, eventually, the ability to carry out the simplest tasks. In most people with the disease, symptoms first appear in their mid-60s. Alzheimer’s disease is the most common cause of dementia among older adults. 

Memory problems are typically one of the first signs of Alzheimer’s. A decline in other aspects of thinking, such as finding the right words, vision or spatial issues, and impaired reasoning or judgment, may also signal the very early stages of Alzheimer’s disease. Mild cognitive impairment is a condition that can be an early sign of Alzheimer’s, but not everyone with mild cognitive impairment will develop the disease.

People with Alzheimer’s have trouble doing everyday things like driving a car, cooking a meal, or paying bills. They may ask the same questions over and over, get lost easily, lose things or put them in odd places, and find even simple things confusing. As the disease progresses, some people become worried, angry, or violent.

What is happening inside the brain of someone living with Alzheimer’s disease?  And are these brain changes fundamentally different to what you see during healthy ageing? During healthy ageing there is some brain shrinkage, but you do not lose large numbers of neurons. In Alzheimer’s disease, however, brain damage is widespread, and many neurons stop functioning, lose connections with other neurons, and die.

Abnormal levels of a sticky protein called beta-amyloid clump together between neurons and disrupt neuron function. Abnormal accumulation of a protein called tau gathers together inside neurons and block the communication between neurons. And, unfortunately, people with dementia seldom have only Alzheimer’s-related changes in their brain. Any number of problems that affect blood vessels, such as hardening of the arteries and mini-strokes—may also be at play.

In Alzheimer’s disease, as neurons are injured and die throughout the brain, connections between networks of neurons may break down, and many brain regions begin to shrink. By the final stages of Alzheimer’s, this process—called brain atrophy—is widespread, causing significant loss of brain volume.

This ruthless disease typically destroys neurons and their connections in parts of the brain involved in memory, including the entorhinal cortex and hippocampus. It later affects areas in the cerebral cortex responsible for language, reasoning, and social behaviour. Eventually, many other areas of the brain are damaged. Over time, a person with Alzheimer’s gradually loses his or her ability to live and function independently. Ultimately, and sadly, Alzheimer’s disease is fatal!

Mental disorders, sometimes called mental illnesses or psychiatric disorders are conditions that affect your thinking, feeling, mood, and behaviour. They may be occasional or long-lasting. They can affect your ability to relate to others and function each day. There are many different types of mental disorders, including depression, anxiety, eating disorders, personality disorders, post-traumatic stress and psychosis.

There is no single cause of mental illness. A number of factors can contribute to your risk of becoming mentally ill, including your genes and family history, life experiences, such as stress or a history of abuse, especially if they happen in childhood, chemical imbalances in the brain, traumatic brain injury, use of alcohol and recreational drugs, physical illness and feeling lonely and isolated.

Depression is the most common form of mental illness.  Globally, 300 million people of all ages suffer from depression. People who suffer with depression often suffer with another mental disorder, like anxiety.

What is depression? Depression is a mood disorder that affects the way you think, feel, and behave. It causes feelings of sadness or hopelessness that can last anywhere from a few days to a few years. This is different from being upset about a minor setback or disappointment in your day.  Some people may experience mild depression only once in their lives, while others have several severe episodes over their lifetime. This more serious, long-lasting and intense form of depression is known as major depressive disorder (MDD). It may also be referred to as clinical depression or major depression.  

How does depression affect the brain? There are three parts of the brain that play a role in major depression: the hippocampus, which stores memories; the amygdala, which facilitates our emotional responses, and the prefrontal cortex, which regulates our emotional responses and decision making. In people with depression, the body releases excessive amounts of a stress hormone called cortisol. This causes neurons in the hippocampus and prefrontal cortex to shrink and the amygdala to do the opposite and become enlarged and more active. The change in the physical structure and chemical activities of these brain structures leads to memory problems, a lack of emotional control, poorly regulated decision-making and disturbed sleeping patterns. 

How can treatment change the brain? Balancing the amount of cortisol and other chemicals in the brain can help reverse any shrinkage of the hippocampus and treat the memory problems it may cause. Correcting the body’s chemical levels can also help reduce symptoms of MDD. 

There are several common medications that can fight the negative effects of depression on the brain by helping to balance the levels chemicals in the brain, like serotonin, norepinephrine and dopamine. Besides medications, psychotherapy can help relieve major depression by changing the structure and function of the prefrontal cortex and it control over the amygdala. 

We have discussed three of the most common ways in which your brain stops functioning normally because it has become injured or diseased. Brain injury, neurodegenerative disease and mental disorders all change the structure and function of the brain and how it contols the body via the nervous system These changes to the brain and nervous system can fundamentally change someone’s behaviour, including their memory, emotions and personality and permanently change how they live their life and well-being.

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