Symptoms are not limited to but may include:

- Increased general confusion as natural light begins to fade and increased shadows appear.

- Agitation and mood swings. Individuals may become fairly frustrated with their own confusion as well as aggravated by noise. Individuals found yelling and becoming increasingly upset with their caregiver is not uncommon.

- Mental and physical fatigue increase with the setting of the sun. This fatigue can play a role in the individual's irritability.

- Tremors may increase and become uncontrollable.

- An individual may experience an increase in their restlessness while trying to sleep. Restlessness can often lead to pacing and or wandering which can be potentially harmful for an individual in a confused state.

The symptoms of dementia vary across types and stages of the diagnosis. The most common affected areas include memory, visual-spatial, language, attention and problem solving. Most types of dementia are slow and progressive. By the time the person shows signs of the disorder, the process in the brain has been happening for a long time. It is possible for a patient to have two types of dementia at the same time. About 10% of people with dementia have what is known as "mixed dementia", which is usually a combination of Alzheimer's disease and another type of dementia such as frontotemporal dementia or vascular dementia. Additional psychological and behavioral problems that often affect people who have dementia include:

- Balance problems

- Tremor

- Speech and language difficulty

- Trouble eating or swallowing

- Memory distortions (believing that a memory has already happened when it has not, thinking an old memory is a new one, combining two memories, or confusing the people in a memory)

- Wandering or restlessness

- Perception and visual problems

- "Behavioral and psychological symptoms of dementia" (BPSD) almost always occur in all types of dementia. BPSDs may manifest as:

When people with dementia are put in circumstances beyond their abilities, there may be a sudden change to crying or anger (a ""catastrophic reaction"").

Psychosis (often delusions of persecution) and agitation/aggression also often accompany dementia.

The presenting symptom of dementia with Lewy bodies is often cognitive dysfunction, though dementia eventually occurs in all individuals with DLB. In contrast to Alzheimer's disease (AD), in which memory loss is the first symptom, those with DLB first experience impaired attention, executive function, and visuospatial function, while memory is affected later. These impairments present as driving difficulty, such as becoming lost, misjudging distances, or as impaired job performance. In terms of cognitive testing, individuals may have problems with figure copying as a result of visuospatial impairment, with clock-drawing due to executive function impairment, and difficulty with serial sevens as a result of impaired attention. Short-term memory and orientation to time and place remain intact in the earlier stages of the disease.

While the specific symptoms in a person with DLB may vary, core features include: fluctuating cognition with great variations in attention and alertness from day to day and hour to hour, recurrent visual hallucinations (observed in 75% of people with DLB), and motor features of Parkinson's disease. Suggestive symptoms are rapid eye movement (REM)-sleep behavior disorder and abnormalities detected in PET or SPECT scans. REM sleep behavior disorder (RBD) often is a symptom first recognized by the patient's caretaker. RBD includes vivid dreaming, with persistent dreams, purposeful or violent movements, and falling out of bed. Benzodiazepines, anticholinergics, surgical anesthetics, some antidepressants, and over-the-counter drug cold remedies may cause acute confusion, delusions, and hallucinations.

Tremors are less common in DLB than in Parkinson's disease. Parkinsonian features may include shuffling gait, reduced arm-swing during walking, blank expression (reduced range of facial expression), stiffness of movements, ratchet-like cogwheeling movements, low speech volume, sialorrhea, and difficulty swallowing. Also, DLB patients often experience problems with orthostatic hypotension, including repeated falls, fainting, and transient loss of consciousness. Sleep-disordered breathing, a problem in multiple system atrophy, also may be a problem.

One of the most critical and distinctive clinical features of the disease is hypersensitivity to neuroleptic and antiemetic medications that affect dopaminergic and cholinergic systems. In the worst cases, a patient treated with these medications could become catatonic, lose cognitive function, or develop life-threatening muscle rigidity. Some commonly used medications that should be used with great caution, if at all, for people with DLB, are chlorpromazine, haloperidol, or thioridazine.

Visual hallucinations in people with DLB most commonly involve perception of people or animals that are not there, and may reflect Lewy bodies or AD pathology in the temporal lobe. Delusions may include reduplicative paramnesia and other elaborate misperceptions or misinterpretations. These hallucinations are not necessarily disturbing, and in some cases, the person with DLB may have insight into the hallucinations and even be amused by them, or be conscious they are not real. People with DLB also may have problems with vision, including double vision, and misinterpretation of what they see, for example, mistaking a pile of socks for snakes or a clothes closet for the bathroom.

In the first stages of dementia, the signs and symptoms of the disorder may be subtle. Often, the early signs of dementia only become apparent when looking back in time. The earliest stage of dementia is called mild cognitive impairment (MCI). 70% of those diagnosed with MCI progress to dementia at some point. In MCI, changes in the person's brain have been happening for a long time, but the symptoms of the disorder are just beginning to show. These problems, however, are not yet severe enough to affect the person’s daily function. If they do, it is considered dementia. A person with MCI scores between 27 and 30 on the Mini-Mental State Examination (MMSE), which is a normal score. They may have some memory trouble and trouble finding words, but they solve everyday problems and handle their own life affairs well.

Agitation often accompanies dementia and often precedes the diagnosis of common age-related disorders of cognition such as Alzheimer's disease (AD). More than 80% of people who develop AD eventually become agitated or aggressive.

It is important to rule out infection and other environmental causes of agitation, such as disease or other bodily discomfort, before initiating any intervention. If no such explanation is found, it is important to support caregivers and educate them about simple strategies such as distraction that may delay the transfer to institutional care (which is often triggered by the onset of agitation).

Sundowning, or sundown syndrome, is a neurological phenomenon associated with increased confusion and restlessness in patients with delirium or some form of dementia. Most commonly associated with Alzheimer's disease, but also found in those with other forms of dementia, the term "sundowning" was coined due to the timing of the patient's confusion. For patients with sundowning syndrome, a multitude of behavioral problems begin to occur in the evening or while the sun is setting. Sundowning seems to occur more frequently during the middle stages of Alzheimer's disease and mixed dementia. Patients are generally able to understand that this behavioral pattern is abnormal. Sundowning seems to subside with the progression of a patient's dementia. Research shows that 20–45% of Alzheimer's patients will experience some sort of sundowning confusion.

Dementia with Lewy bodies (DLB) is a type of dementia that worsens over time. Additional symptoms may include fluctuations in alertness, visual hallucinations, slowness of movement, trouble walking, and rigidity. Excessive movement during sleep and mood changes such as depression are also common.

The cause is unknown. Typically, no family history of the disease exists among those affected. The underlying mechanism involves the buildup of Lewy bodies, clumps of alpha-synuclein protein in neurons. It is classified as a neurodegenerative disorder. A diagnosis may be suspected based on symptoms, with blood tests and medical imaging done to rule out other possible causes. The differential diagnosis includes Parkinson's and Alzheimer's.

At present there is no cure. Treatments are supportive and attempt to relieve some of the motor and psychological symptoms associated with the disease. Acetylcholinesterase inhibitors, such as donepezil, may provide some benefit. Some motor problems may improve with levodopa. Antipsychotics, even for hallucinations, should generally be avoided due to side effects.

DLB is the most common cause of dementia after Alzheimer's disease and vascular dementia. It typically begins after the age of 50. About 0.1% of those over 65 are affected. Men appear to be more commonly affected than women. In the late part of the disease, people may depend entirely on others for their care. Life expectancy following diagnosis is about eight years. The abnormal deposits that cause the disease were discovered in 1912 by Frederic Lewy.

Causes include:

- Schizophrenia

- Bipolar disorder

- Excited delirium

- Post-traumatic stress disorder (PTSD)

- Panic attacks

- Anxiety disorder

- Obsessive-compulsive disorder (OCD)

- Alcohol withdrawal

- Claustrophobia

- Dementia

- Parkinson's disease

- Traumatic brain injury

- Alzheimer's disease

- Acute intermittent porphyria

- Hereditary coproporphyria

- Variegate porphyria

- Side effects of drugs like cocaine or methylphenidate

- Side effects of antipsychotics like haloperidol

The history of disturbance in pseudodementia is often short and abrupt onset, while dementia is more often insidious. Clinically, people with pseudodementia differ from those with true dementia when their memory is tested. They will often answer that they don't know the answer to a question, and their attention and concentration are often intact, and they may appear upset or distressed. Those with true dementia will often give wrong answers, have poor attention and concentration, and appear indifferent or unconcerned.

Investigations such as SPECT imaging of the brain show reduced blood flow in areas of the brain in people with Alzheimer's disease, compared with a more normal blood flow in those with pseudodementia.

Pseudodementia is a phenotype approximated by a wide variety of underlying disorders (1). Data indicate that some of the disorders that can convert to a pseudodementia-like presentation include depression (mood), schizophrenia, mania, dissociative disorders, Ganser syndrome, conversion reaction, and psychoactive drugs (2). Although the frequency distribution of disorders presenting as pseudodementia remains unclear, what is clear is that depressive pseudodementia, synonymously referred to as depressive dementia(3) or major depression with depressive dementia (4), represents a major subclass of the overarching category of pseudodementia (4).

It has long been observed that in the differential diagnosis between dementia and pseudodementia, depressive pseudodementia appears to be the single most difficult disorder to distinguish from nosologically established "organic" categories of dementia(5), especially degenerative dementia of the Alzheimer type (6).

Depressive Pseudodementia is a syndrome seen in older people in which they exhibit symptoms consistent with dementia but the cause is actually depression.

Older people with predominant cognitive symptoms such as loss of memory, and vagueness, as well as prominent slowing of movement and reduced or slowed speech, were sometimes misdiagnosed as having dementia when further investigation showed they were suffering from a major depressive episode. This was an important distinction as the former was untreatable and progressive and the latter treatable with antidepressant therapy or electroconvulsive therapy or both. In contrast to major depression, dementia is a progressive neurodegenerative syndrome involving a pervasive impairment of higher cortical functions resulting from widespread brain pathology.

Psychomotor agitation is a set of signs and symptoms that stem from mental tension and anxiety. The signs are unintentional and purposeless motions; the symptoms are emotional distress and restlessness. Typical manifestations include pacing around a room, wringing the hands, uncontrolled tongue movement, pulling off clothing and putting it back on, and other similar actions. In more severe cases, the motions may become harmful to the individual, such as ripping, tearing, or chewing at the skin around one's fingernails, lips, or other body parts to the point of bleeding. Psychomotor agitation is typically found in major depressive disorder or obsessive-compulsive disorder, and sometimes the manic phase in bipolar disorder, though it can also be a result of an excess intake of stimulants. It can also be caused by severe hyponatremia. The middle-aged and the elderly are more at risk to express it.

Differentiating the different dementia syndromes can be challenging, due to the frequently overlapping clinical features and related underlying pathology. In particular, Alzheimer's dementia often co-occurs with vascular dementia.

People with vascular dementia present with progressive cognitive impairment, acutely or subacutely as in mild cognitive impairment, frequently step-wise, after multiple cerebrovascular events (strokes). Some people may appear to improve between events and decline after more silent strokes. A rapidly deteriorating condition may lead to death from a stroke, heart disease, or infection.

Signs and symptoms are cognitive, motor, behavioral, and for a significant proportion of patients also affective. These changes typically occur over a period of 5–10 years. Signs are typically the same as in other dementias, but mainly include cognitive decline and memory impairment of sufficient severity as to interfere with activities of daily living, sometimes with presence of focal neurologic signs, and evidence of features consistent with cerebrovascular disease on brain imaging (CT or MRI). The neurologic signs localizing to certain areas of the brain that can be observed are hemiparesis, bradykinesia, hyperreflexia, extensor plantar reflexes, ataxia, pseudobulbar palsy, as well as gait and swallowing difficulties. People have patchy deficits in terms of cognitive testing. They tend to have better free recall and fewer recall intrusions when compared with patients with Alzheimer's disease. In the more severely affected patients, or patients affected by infarcts in Wernicke's or Broca's areas, specific problems with speaking called dysarthrias and aphasias may be present.

In small vessel disease, the frontal lobes are often affected. Consequently, patients with vascular dementia tend to perform worse than their Alzheimer's disease counterparts in frontal lobe tasks, such as verbal fluency, and may present with frontal lobe problems: apathy, abulia, problems with attention, orientation, and urinary incontinence. They tend to exhibit more perseverative behavior. VaD patients may also present with general slowing of processing ability, difficulty shifting sets, and impairment in abstract thinking. Apathy early in the disease is more suggestive of vascular dementia.

Rare genetic disorders which result in vascular lesions in the brain have other patterns of presentation. As a rule, they tend to present earlier in life and have a more aggressive course. In addition, infectious disorders, such as syphilis, can lead to arterial damage, strokes, and bacterial inflammation of the brain.

Cognitive symptoms from steroids appear within the first few weeks of treatment, appear to be dose dependent, and may or may not be accompanied by steroid psychosis or other Cushing's-type symptoms.

The symptoms include deficits in

- verbal and non-verbal memory

- working memory

- attention

- sustained concentration

- executive function

- psychomotor speed

- academic or occupational performance.

These symptoms have been shown to improve within months to a year after discontinuing glucocorticoid medication, but residual impairments following prolonged steroid use can remain.

Mild and major neurocognitive disorders are usually associated with but not restricted to the elderly. Unlike delirium, conditions under these disorders develop slowly and are characterized by memory loss. In addition to memory loss and cognitive impairment, other symptoms include aphasia, apraxia, agnosia, loss of abstract thought, behavioral/personality changes, and impaired judgment. There may also be behavioral disturbances including psychosis, mood, and agitation.

Mild and major neurocognitive disorders are differentiated based on the severity of their symptoms. Previously known as dementia, major neurocognitive disorder is characterized by significant cognitive decline and interference with independence, while mild neurocognitive disorder is characterized by moderate cognitive decline and does not interfere with independence. To be diagnosed, it must not be due to delirium or other mental disorder. They are also usually accompanied by another cognitive dysfunction. For non-reversible causes of dementia such as age, the slow decline of memory and cognition is lifelong. It can be diagnosed by screening tests such as the Mini Mental State Examination (MMSE).

Patients with psychoorganic syndrome often complain about headaches, dizziness, unsteadiness when walking, poor tolerance to the heat, stuffiness, atmospheric pressure changes, loud sounds, neurological symptoms.

The common reported psychological symptoms include:

- loss of memory and concentration

- emotional liability

- Clinical fatigue

- long term major depression

- severe anxiety

- reduced intellectual ability

The cognitive and behavioral symptoms are chronic and have little response to treatment.

Depending on lesion location, some patients may experience visual complications.

The first symptoms are often mistakenly attributed to ageing or stress. Detailed neuropsychological testing can reveal mild cognitive difficulties up to eight years before a person fulfils the clinical criteria for diagnosis of AD. These early symptoms can affect the most complex activities of daily living. The most noticeable deficit is short term memory loss, which shows up as difficulty in remembering recently learned facts and inability to acquire new information.

Subtle problems with the executive functions of attentiveness, planning, flexibility, and abstract thinking, or impairments in semantic memory (memory of meanings, and concept relationships) can also be symptomatic of the early stages of AD. Apathy can be observed at this stage, and remains the most persistent neuropsychiatric symptom throughout the course of the disease. Depressive symptoms, irritability and reduced awareness of subtle memory difficulties are also common.

The preclinical stage of the disease has also been termed mild cognitive impairment (MCI). This is often found to be a transitional stage between normal ageing and dementia. MCI can present with a variety of symptoms, and when memory loss is the predominant symptom, it is termed "amnestic MCI" and is frequently seen as a prodromal stage of Alzheimer's disease.

During the final stages, the patient is completely dependent upon caregivers. Language is reduced to simple phrases or even single words, eventually leading to complete loss of speech. Despite the loss of verbal language abilities, people can often understand and return emotional signals. Although aggressiveness can still be present, extreme apathy and exhaustion are much more common symptoms. People with Alzheimer's disease will ultimately not be able to perform even the simplest tasks independently; muscle mass and mobility deteriorates to the point where they are bedridden and unable to feed themselves. The cause of death is usually an external factor, such as infection of pressure ulcers or pneumonia, not the disease itself.

Vascular dementia, also known as multi-infarct dementia (MID) and vascular cognitive impairment (VCI), is dementia caused by problems in the supply of blood to the brain, typically a series of minor strokes, leading to worsening cognitive decline that occurs step by step. The term refers to a syndrome consisting of a complex interaction of cerebrovascular disease and risk factors that lead to changes in the brain structures due to strokes and lesions, and resulting changes in cognition. The temporal relationship between a stroke and cognitive deficits is needed to make the diagnosis.

Delirium can be caused by the worsening of previous medical conditions, substance abuse or withdrawal, mental illness, severe pain, immobilization, sleep deprivation and hypnosis.

Other common causes that may increase the risk of delirium include infections of urinary tract, skin and stomach, pneumonia, old age, and poor nutrition.

Pseudosenility also reversible dementia is a condition where older people are in a state of memory loss, confusion, or disorientation that may have a cause other than the ordinary aging process. Generally, the term "reversible dementia" is used to describe most cases. A more specific term "Pseudodementia" is referring to "behavioral changes that resembler those of the progressive degenerative dementias, but which are attributable to so-called functional causes".

The "New York Times" reports that illnesses such as the flu and hydrocephalus, as well as side-effects to common medications, can produce symptoms in the elderly that are difficult to distinguish from ordinary dementia caused by aging. However, if the real cause of the effects is caught early enough, the effects can be reversed. According to studies cited in Cunha (1990), approximate 10% to 30% of patients who have exhibited symptoms of dementia might have a treatable or reversible pathologic process to some extent.

Alcohol-related dementia presents as a global deterioration in intellectual function with memory not being specifically affected, but it may occur with other forms of dementia, resulting in a wide range of symptoms. Certain individuals with alcohol-related dementia present with damage to the frontal lobes of their brain causing disinhibition, loss of planning and executive functions, and a disregard for the consequences of their behavior. Other types of alcohol-related dementia such as Korsakoff's Syndrome cause the destruction of certain areas of the brain, where changes in memory, primarily a loss of short term memory, are the main symptom. Most presentations of alcohol dementia are somewhere along the spectrum between a global dementia and Korsakoff's psychosis, and may include symptoms of both.

Individuals affected by alcohol-related dementia may develop memory problems, language impairment, and an inability to perform complex motor tasks such as getting dressed. Heavy alcohol abuse also damages the nerves in arms and legs, i.e. peripheral neuropathy, as well as the cerebellum that controls coordination thereby leading to the development of cerebellar ataxia. These patients frequently have problems with sensation in their extremities and may demonstrate unsteadiness on their feet.

Alcohol-related dementia can produce a variety of psychiatric problems including psychosis (disconnection from reality), depression, anxiety, and personality changes. Patients with alcoholic dementia often develop apathy, related to frontal lobe damage, that may mimic depression. People with alcoholism are more likely to become depressed than people without alcoholism, and it may be difficult to differentiate between depression and alcohol dementia.

Symptoms include mental deterioration, language disorder, transient ischemic attack, muscle ataxia, and impaired movements including change of walk, slowness of movements, and change in posture. These symptoms usually coincide with multiple falls, epilepsy, fainting, and uncontrollable bladder.

Because Binswanger’s disease affects flow processing speed and causes impaired concentration, the ability to do everyday tasks such as managing finances, preparing a meal and driving may become very difficult.

FTD is traditionally difficult to diagnose due to the heterogeneity of the associated symptoms. Signs and symptoms are classified into three groups based on the functions of the frontal and temporal lobes:

- Behavioural variant frontotemporal dementia (BvFTD) is characterized by changes in social behavior and conduct, with loss of social awareness and poor impulse control.

- Semantic dementia (SD) is characterized by the loss of semantic understanding, resulting in impaired word comprehension, although speech remains fluent and grammatically faultless.

- Progressive nonfluent aphasia (PNFA) is characterized by progressive difficulties in speech production.

However, the following abilities in the person with FTD are preserved:

- Perception

- Spatial Skills

- Memory

- Praxis

In later stages of FTD, the clinical phenotypes may overlap. FTD patients tend to struggle with binge eating and compulsive behaviors. These binge eating habits are often associated with abnormal eating behavior including overeating, stuffing oneself with food, changes in food preferences (cravings for more sweets, carbohydrates), eating inedible objects and snatching food from others. Recent findings from structural MRI research have indicated that eating changes in FTD are associated with atrophy (wasting) in the right ventral insula, striatum, and orbitofrontal cortex.

Patients with FTD show marked deficiencies in executive functioning and working memory. Most FTD patients become unable to perform skills that require complex planning or sequencing. In addition to the characteristic cognitive dysfunction, a number of primitive reflexes known as frontal release signs are often able to be elicited. Usually the first of these frontal release signs to appear is the palmomental reflex which appears relatively early in the disease course whereas the palmar grasp reflex and rooting reflex appear late in the disease course.

In rare cases, FTD can occur in patients with motor neuron disease (MND) (typically amyotrophic lateral sclerosis). The prognosis for people with MND is worse when combined with FTD, shortening survival by about a year.

Steroid dementia syndrome describes the signs and symptoms of hippocampal and prefrontal cortical dysfunction, such as deficits in memory, attention, and executive function, induced by glucocorticoids. Dementia-like symptoms have been found in some individuals who have been exposed to glucocorticoid medication, often dispensed in the form of asthma, arthritis, and anti-inflammatory steroid medications. The condition reverses, but not always completely, within months after steroid treatment is stopped.

The term "steroid dementia" was coined by Varney et al. (1984) in reference to the effects of long-term glucocorticoid use in 1,500 patients. While the condition generally falls under the classification of Cushing's syndrome, the term "steroid dementia syndrome" is particularly useful because it recognizes both the cause of the syndrome and the specific effects of glucocorticoids on cognitive function. Further, the more precise terminology clearly distinguishes the condition from full-blown Cushing's syndrome, which is extremely broad regarding the causes (endogenous or exogenous, pituitary or adrenal) and the multitude of symptoms (ranging from skin disorders to osteoporosis), and from hypercortisolemia, which identifies neither the source nor the symptoms of excess circulatory cortisol.