The Diagnostic and Statistical Manual of Mental Disorders has broken up the diagnoses that once fell under the diagnostic category organic mental disorder into three categories: delirium, dementia, and amnestic. Delirium
Delirium or Acute organic brain syndrome is a recently appearing state of mental impairment, as a result of intoxication, drug overdose, infection, pain, and many other physical problems affecting mental status. In medical contexts, "acute" means "of recent onset". As is the case with most acute disease problems, acute organic brain syndrome is often temporary, although this does not guarantee that it will not recur or progress to become chronic, that is, long-term. A more specific medical term for the acute subset of organic brain syndromes is delirium. Thinking, remembering, sleeping, and paying attention can become difficult during alcohol withdrawal, after surgery, or with dementia. Dementia
Dementia or chronic organic brain syndrome is long-term. For example, some forms of chronic drug or alcohol dependence can cause organic brain syndrome due to their long-lasting or permanent toxic effects on brain function. Other common causes of chronic organic brain syndrome sometimes listed are the various types of dementia, which result from permanent brain damage due to strokes, Alzheimers disease, or other damaging causes which are irreversible. Amnestic pertains to amnesia and is the impairment in ability to learn or recall new information, or recall previously learned information. Although similar, it is not coupled with dementia or delirium. Amnestic
Amnestic conditions denotes a gray zone between delirium and dementia; its early course may fluctuate, but it is often persistent and progressive.
Damage to brain functioning could be due not only to organic (physical) injury (a severe blow to the head, stroke, chemical and toxic exposures, organic brain disease, substance use, etc.) and also to non-organic means such as severe deprivation, abuse, neglect, and severe psychological trauma. Symptoms
Many of the symptoms of Organic Mental Disorder depend on the cause of the disorder, but are similar and include physical or behavioral elements. Dementia and delirium are the cause of the confusion, orientation, cognition or alertness impairment. Therefore, these symptoms require more attention because hallucinations, delusions, amnesia, and personality changes are the result. These effects of the dementia and delirium are not joined with the changes of sensory or perception abilities. Memory impairment, judgment, logical function and agitation are also some extremely common symptoms. The more common symptoms of OBS are confusion; impairment of memory, judgment, and intellectual function;  and agitation. Often these symptoms are attributed to psychiatric illness, which causes a difficulty in diagnosis. Associated conditions
Disorders that are related to injury or damage to the brain and contribute to OBS include, but are not limited to:

Alcoholism
Alzheimers disease
Attention deficit/hyperactivity disorder
Autism
Concussion
Encephalitis
Epilepsy
Fetal alcohol syndrome
Hypoxia
Parkinsons disease
Intoxication/overdose caused by substance use disorders including alcohol use disorder
Non-medical use of sedative hypnotics
Intracranial hemorrhage/trauma
Korsakoff syndrome
Mastocytosis
Meningitis
Psychoorganic syndrome
Stroke/transient ischemic attack (TIA)
Withdrawal from drugs, especially sedative hypnotics, e.g. alcohol or benzodiazepinesOther conditions that may be related to organic brain syndrome include: clinical depression, neuroses, and psychoses, which may occur simultaneously with the OBS.