At its basic level, the term cognitive disorder applies to any type of disorder, disease, or condition that impairs the cognitive functioning of the person. This results in the person's ability to function becoming extremely difficult or impossible without treatment or without some form of help. Cognition is a term that refers to:
- various mental functions such as learning and memory
- perceiving or identifying and understanding the relationships of objects in one's environment
- solving problems
- understanding language
- communicating with others
- making decisions
- being able to think about things from different viewpoints.
People with cognitive disorders have issues that affect their ability to perform one or more of these actions.
According to the American Psychiatric Association's (APA) Diagnostic and Statistical Manual of Mental Disorders - Fifth Edition (DSM-5) cognitive disorders are now listed as neurocognitive disorders to indicate that there is some type of involvement of the brain. The main neurocognitive disorders listed in the DSM-5 are:
Delirium: A change in thinking that develops over a short period of time and includes a loss of awareness of a person's surroundings, situation, and ability to think clearly.
Dementia: A progressive decline in a person's thinking that most often includes memory loss, problems concentrating, and a loss of other thinking capabilities.
Amnesia: Memory loss without a significant loss of other thinking abilities.
Others: Many other conditions that can be due to medical conditions, the use of drugs, etc.
There are many other possible causes and types of cognitive disorders. It would take an entire book to list all the possible causes of cognitive disorders and the causes of what is often referred to as cognitive dysfunction. Cognitive dysfunction is a change in thinking like the changes that happen in cognitive disorders but is not a diagnosable disorder like dementia. Some of the major causes of cognitive disorders/dysfunction include:
Genes: Genetic influences appear to play a role in many different cognitive disorders. For instance, Huntington's disease is a severe movement disorder that often includes significant changes in thinking. The dementia that comes along with the disorder is believed to be due to genetic causes. Even Alzheimer's disease is believed to have possible genetic causes in some people that develop the disorder. Strokes happen when the blood supply to the brain is disrupted because of ruptured or blocked veins or arteries in the brain. Strokes often produce significant cognitive dysfunction in people. Strokes are believed to be the result of a combination of genetic factors and one's behavior such as diet, lifestyle, certain health conditions, etc. Developmental disorders such as Down syndrome often produce significant cognitive dysfunction and often are the result of genetic factors.
Head Injury: Head injuries can produce significant cognitive dysfunction. They can be a source of disorders like dementia or amnesia. Depending on the severity and extent of the head injury the effects can be specific to the part of the brain that is injured or can affect one's overall functioning. Closed head injuries often produce traumatic brain injuries (TBIs) that happen when the brain is not penetrated by some object. These types of injuries include concussions (when the brain is either shaken or bounces against the skull), bruises to the brain (known as hematomas), and other similar types of injuries. A person with a traumatic brain injury may only display cognitive issues associated with the area of the brain that has been affected, or may display many problems with thinking. Penetrating head injuries, such as being shot in the head, often only affect the area of the brain that has been damaged and may or may not lead to overall problems with thinking.
Diseases and Infections: There are many bacteria, viruses, and disease conditions that can affect the brain and lead to cognitive dysfunction or a cognitive disorder. Meningitis is an inflammation of the protective covering of the brain and spinal cord that can be caused by bacteria or a virus. It can lead to significant cognitive dysfunction and even death. Multiple sclerosis (MS) is a disease that is believed to happen when the body's immune system begins to attack a substance known as myelin. Myelin is a part of the cells in the central nervous system (the brain and spinal cord) that help the cells to signal to one another. When the myelin is severely damaged, the cells cannot communicate, and people begin to have problems with their thinking and movement. Parkinson's disease happens when the cells in the brain that produce a chemical known as dopamine begin to die. The cells that use dopamine cannot communicate effectively with one another. Some people with Parkinson's disease may develop dementia because of these changes in the brain. People who contract AIDS often begin to experience cognitive dysfunction. They may even develop dementia because of the virus associated with AIDS.
Brain Tumors: Tumors are abnormal cells that grow and penetrate the areas of the body where they are located. Tumors can either be benign or malignant. Benign means that they will not spread to other areas. Malignant means that they will spread to other areas and may continue to grow even after most of the tumor is removed. Tumors that happen in the brain or in the coverings of the brain can affect the area of the brain where they are located. This can result in cognitive dysfunction associated with that area of the brain. For example, a tumor that is in a person's speech center can affect their ability to speak and understand language, but may not affect other functions. Tumors can also affect other areas in the brain if they grow in multiple areas of the brain or if they become so big that they begin to push the brain up against the skull and affect other areas of the brain. Even surgery to remove the tumors may not result in a person regaining all the cognitive functions that were affected by the tumor.
Exposure to Toxic Substances: There are many substances that can affect the functioning of the brain and lead to cognitive disorders or cognitive dysfunction. These substances are often referred to as neurotoxins. People exposed to lead or other heavy metals can develop issues with their memory and other cognitive functions. Being exposed to paint fumes, the fumes from certain types of glues, cements, gasoline or aerosol cans, etc. can also result in significant brain damage. This damage can lead to cognitive dysfunction. The use of alcohol or drugs like cocaine or heroin can result in significant cognitive dysfunction or the development of a cognitive disorder. For example, some people who abuse alcohol over time may develop a form of dementia due to brain damage related to their alcohol abuse.
Malnutrition or other Lifestyle Factors: Not eating properly, getting sufficient exercise, or other factors associated with the person's lifestyle can lead to the development of a cognitive disorder. For instance, a condition known as Wernicke Korsakoff syndrome that often is diagnosed in people with severe alcoholism. This happens because of a very poor diet and not because of their alcohol abuse. People that develop this condition lack vitamin B1 because of a poor diet. This can affect the functioning of the brain and lead to severe problems with memory and other issues. If the person does not fix their diet and get proper nutrition the changes can become permanent. People that are obese are also vulnerable to many different types of cognitive disorders such as stroke and even dementia. Severe malnutrition can lead to issues with delirium.
These conditions only represent a few of the many that can lead to cognitive disorders. In this topic center, you'll find more information about cognitive disorders and some of their causes.