Cognition is the brain's ability to retain and use information. A cognitive disorder refers to any medical condition that affects the way the brain processes and stores information. It can cause memory loss, faulty perceptions, or a combination of both. Cognitive disorders can be genetic, environmental, or caused by injury.
Delirium is a cognitive disorder that appears in episodes and can be temporary or recurrent. It impairs the brain's ability to process new information or be aware of its surroundings. Hypoactive delirium is when a person who is unaware of their surroundings appears to be lethargic or unresponsive, while episodes of hyperactive delirium make a person hostile or aggressive. Mixed delirium is a combination of hypoactive and hyperactive symptoms. Delirium does not have a definitive cause, although stress, alcohol, or medication may contribute to episodes.
Although delirium is temporary, it can develop into dementia over time in some people. Dementia is an incurable cognitive disorder that usually causes partial or total memory loss. The disorder also makes it difficult to learn new information and can inhibit the brain's ability to assess the environment and make judgments. Dementia can be genetic or caused by brain trauma, stroke, or heart valve infection. Alzheimer's disease is one of the most common forms of dementia and generally affects people over the age of 60.
Amnestic disorder, more commonly known as amnesia, is a cognitive disorder in which a person no longer has long-term memories or is unable to retain short-term memories. A person with this disorder is usually coherent, unlike other cognitive disorders. Amnestic disorder can be caused by trauma or damage to the brain, such as infection, loss of oxygen, or tumors.
A cognitive disorder that can occur in fetuses or young children is mental retardation. It is a condition in which a person has low cognitive abilities due to developmental delays. He or she cannot learn new concepts or functions at the same level as other people his or her age. Although the severity of mental retardation can vary, many people with the condition do not have the mental skills to care for themselves safely.
Mental retardation is usually diagnosed in children and is usually a condition they are born with or develop as infants. It can be caused by a variety of bacterial infections while in the womb or shortly after birth. Serious head injuries or nutritional deficiencies can cause a baby to be mentally retarded; However, many cases of mental retardation do not have definitive causes.