Cognitive disorders (CDs), also known as neurocognitive disorders (NCDs), are a category of mental health disorders that primarily affect cognitive abilities including learning, memory, perception, and problem solving. Neurocognitive disorders include delirium, mild neurocognitive disorders, and major neurocognitive disorder (previously known as dementia). They are defined by deficits in cognitive ability that are acquired (as opposed to developmental), typically represent decline, and may have an underlying brain pathology. The DSM-5 defines six key domains of cognitive function: executive function, learning and memory, perceptual-motor function, language, complex attention, and social cognition. Although Alzheimer's disease accounts for the majority of cases of neurocognitive disorders, there are various medical conditions that affect mental functions such as memory, thinking, and the ability to reason, including frontotemporal degeneration, Huntington's disease, dementia with Lewy bodies, traumatic brain injury (TBI), Parkinson's disease, prion disease, and dementia/neurocognitive issues due to HIV infection. Neurocognitive disorders are diagnosed as mild and major based on the severity of their symptoms. While anxiety disorders, mood disorders, and psychotic disorders can also have an effect on cognitive and memory functions, they are not classified under neurocognitive disorders because loss of cognitive function is not the primary (causal) symptom. Additionally, developmental disorders such as autism typically have a genetic basis and become apparent at birth or early in life as opposed to the acquired nature of neurocognitive disorders. Causes vary between the different types of disorders but most include damage to the memory portions of the brain. Treatments depend on how the disorder is caused. Medication and therapies are the most common treatments; however, for some types of disorders such as certain types of amnesia, treatments can suppress the symptoms but there is currently no cure. Classifications The previous edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) included a section entitled "Delirium, Dementia and Amnestic and Other Cognitive Disorders," which was revised in DSM-5 to the broader "Neurocognitive Disorders." Neurocognitive disorders are described as those with "a significant impairment of cognition or memory that represents a marked deterioration from a previous level of function". The main principle distinguishing neurocognitive disorders from mood disorders and other psychiatric conditions that involve a cognitive component (i.e. increased lapses in memory noted by patients with depression) is that cognitive decline is the "defining characteristic" of the disorder. Additionally, the term "neurocognitive" was added because these disorders most often have alterations/disfunction in neural physiology (i.e. amyloid