Delirium: Symptoms, Types, Causes and Treatment

Delirium is a common, serious, and often under-recognized neuropsychiatric syndrome that can have profound consequences for patients and their families. Characterized by a sudden disturbance in attention, awareness, and cognition, delirium affects people of all ages but is especially prevalent among older adults and those who are hospitalized. In this article, we will explore the key symptoms, types, causes, and evidence-based treatments for delirium, synthesizing the most current research to help deepen your understanding of this complex condition.

Symptoms of Delirium

Delirium presents with a striking and acute change in a person’s mental state, impacting their cognition, perception, and behavior. Recognizing the hallmark symptoms is crucial for timely identification and management.

Symptom	Description	Frequency/Notes	Sources
Inattention	Difficulty focusing, sustaining, or shifting attention	Most common and central symptom	1 4 3
Disorientation	Confusion about time, place, or person	Frequently observed	4 3
Disturbed Consciousness	Altered awareness, fluctuating alertness	Ranges from hypervigilance to stupor	1 6 7
Memory Impairment	Problems with short-term memory	Common, especially in adults	4 3
Perceptual Disturbances	Hallucinations, illusions, or misinterpretations	More common in hyperactive forms	4 7
Psychomotor Changes	Agitation or retardation	Hyperactive, hypoactive, or mixed presentation	4 6
Sleep-Wake Disturbance	Fragmented sleep, daytime drowsiness	Noted in both children and adults	3 12

Table 1: Key Symptoms of Delirium

Core Clinical Features

The central features of delirium are inattention and an acute disturbance in awareness. Patients may find it challenging to follow conversations, stay focused, or respond appropriately to their environment. Disorientation—often to time or place—is also a core sign, and these symptoms tend to fluctuate throughout the day, sometimes dramatically 1 4.

Cognitive and Perceptual Changes

Beyond attention and orientation, delirium can affect memory (especially short-term), language, and reasoning. Many patients experience disorganized thinking, which may manifest as rambling or incoherent speech. Perceptual disturbances, such as hallucinations (seeing or hearing things that aren’t there), illusions, or misinterpretations of real stimuli, can be distressing both for patients and caregivers 4 7.

Motor and Behavioral Symptoms

Delirium often includes changes in psychomotor activity. Some people become restless, agitated, or even aggressive (hyperactive delirium), while others become lethargic, slowed, or appear withdrawn (hypoactive delirium). Many experience a mixture of both states (mixed delirium). Sleep-wake cycle disturbances—such as fragmented sleep or reversed day-night patterns—are also common 3 4.

Symptom Variability Across Ages

Symptoms of delirium can look different in children compared to adults. Children may be more irritable, agitated, or display affective lability, whereas adults more frequently experience speech disturbances, delusions, and paranoia. However, disturbances in alertness, anxiety, disorientation, and hallucinations can occur in both groups 3.

Types of Delirium

Delirium is not a uniform condition; it presents in several subtypes, often defined by motor activity and alertness. Understanding these types helps guide both diagnosis and management.

Type	Core Features	Prevalence & Prognosis	Sources
Hyperactive	Agitation, restlessness, hallucinations	Less common, more easily recognized; better prognosis	6 7 9 10
Hypoactive	Lethargy, slowed responses, apathy	Most common; often missed; worse outcomes	6 9 10
Mixed	Alternating hyperactive and hypoactive states	Intermediate prevalence; worst outcomes	6 9 10
Subsyndromal	Some symptoms, but not full criteria	Intermediate risk; can progress to full syndrome	2 4

Table 2: Major Types of Delirium

Hyperactive Delirium

This type is marked by heightened arousal—patients may be restless, agitated, attempt to get out of bed, or experience vivid hallucinations and delusions. Hyperactive delirium is less common but more likely to be recognized due to its disruptive nature 6 7 9.

Hypoactive Delirium

The most prevalent type, especially in older adults and ICU patients, hypoactive delirium is characterized by lethargy, reduced motor activity, and withdrawal. Because these patients are quiet and less demanding, this subtype is easily missed, yet it is associated with higher mortality and worse functional outcomes 9 10.

Mixed Delirium

Many patients cycle between hyperactive and hypoactive states. This mixed type is associated with the longest duration of delirium, highest rates of complications, and the poorest outcomes, including increased mortality and longer hospital stays 9 10.

Subsyndromal Delirium

Some individuals exhibit several delirium symptoms but do not meet full diagnostic criteria. Subsyndromal delirium still carries an increased risk for poor outcomes and may progress to full-blown delirium if unrecognized 2 4.

Clinical and Etiological Relevance

Identifying the specific subtype is not just academic—it can inform prognosis, guide management strategies, and highlight underlying causes, such as drug-induced or metabolic disturbances 7 8. For instance, hypoactive delirium is more common in older, frail patients with high comorbidity, while hyperactive delirium is often seen in alcohol withdrawal 10 7.

Causes of Delirium

Delirium has a multifactorial etiology, with both predisposing vulnerabilities and acute precipitating factors. Understanding these mechanisms is key to prevention and treatment.

Factor	Examples	Mechanism/Notes	Sources
Predisposing	Age, dementia, chronic illness	Increase baseline vulnerability	1 12 13
Precipitating	Infection, surgery, trauma, medications	Acute physiological stressors	1 12 13 14
Neurotransmitter Imbalance	Dopamine excess, acetylcholine deficiency	Disrupted brain signaling	1 11 14
Neuroinflammation	Sepsis, systemic inflammation	Cytokine-mediated brain dysfunction	1 11 12
Metabolic & Vascular	Hypoxia, electrolyte imbalance, stroke	Energy deprivation or vascular injury	1 11 12
Drug Effects	Anticholinergics, benzodiazepines, narcotics	Direct or indirect brain effects	14 13

Table 3: Main Causes and Mechanisms of Delirium

Predisposing and Precipitating Factors

Delirium develops when an acute insult occurs in a vulnerable brain. Predisposing factors—such as advanced age, pre-existing cognitive impairment, or severe chronic illness—increase susceptibility 1 12 13. Superimposed acute triggers include infections (especially urinary tract and respiratory), surgery, metabolic derangements, pain, and drug effects 1 12 13 14.

Neurobiological Mechanisms

Delirium is believed to result from a convergence of several brain disturbances:

• Neurotransmitter Imbalance: Most notably, excess dopamine and reduced acetylcholine are implicated. Imbalances in serotonin, norepinephrine, glutamate, and GABA also play a role, depending on the delirium subtype and cause 11 14.
• Neuroinflammation: Systemic inflammation (e.g., from infection or trauma) can disrupt the blood-brain barrier, leading to brain dysfunction through cytokine release and microglial activation 1 11 12.
• Altered Brain Metabolism: Hypoxia, hypoglycemia, and electrolyte imbalances impair neuronal function, leading to delirium 1 11 12.
• Network Disconnectivity: Acute stress and aging may impair brain network connectivity and increase vulnerability to delirium 11 12.

Drug-Induced Delirium

Drugs are a leading reversible cause, especially in older adults. Medications with anticholinergic properties, benzodiazepines, and opioids can trigger delirium by disrupting neurotransmitter systems and altering brain function 14 13. Awareness of medication effects is crucial for prevention and management.

The "Final Common Pathway"

Although many pathways can lead to delirium, they tend to converge on altered neurotransmitter synthesis, function, and availability, resulting in the complex cognitive and behavioral changes seen in this syndrome 11 1.

Treatment of Delirium

Effective delirium management requires a comprehensive, individualized approach. While pharmacological treatments are often considered, non-drug strategies remain the mainstay of care.

Treatment Type	Examples/Strategies	Efficacy/Notes	Sources
Non-Pharmacological	Treat underlying causes, re-orienting, mobilization	First-line and most effective approach	1 13 17
Medication Review	Stop or minimize deliriogenic drugs	Critical for prevention and resolution	1 14 17
Antipsychotics	Haloperidol, atypical antipsychotics	No clear evidence of benefit; side effects	1 15 16 17 19
Other Medications	Dexmedetomidine, ramelteon (select cases)	Promise in ICU/prevention; more research needed	18 19
Prevention	Early mobility, sleep hygiene, minimize restraints	Reduces incidence and severity	13 1 18

Table 4: Delirium Treatment and Prevention Strategies

Non-Pharmacological Management

The cornerstone of delirium treatment is identifying and correcting underlying causes—such as infections, metabolic derangements, or medication effects. Supportive care includes:

• Re-orienting communication (clocks, calendars, familiar objects)
• Encouraging family engagement
• Promoting sleep hygiene and minimizing nighttime disruptions
• Early mobilization and physical activity
• Ensuring adequate hydration and nutrition
• Managing pain and other distressing symptoms

These multidomain interventions are supported by strong evidence and should be implemented universally 1 13 17.

Medication Review and Withdrawal

A thorough review of the patient’s medication list is essential. Drugs with deliriogenic potential, such as anticholinergics, benzodiazepines, and opioids, should be reduced or discontinued whenever possible 14 1.

Pharmacological Interventions

Antipsychotics

Despite common clinical use, research consistently shows that antipsychotic medications—such as haloperidol and atypical agents—do not reduce delirium severity, resolve symptoms, or affect mortality in non-ICU hospitalized patients. They may be considered for severe agitation or distress that threatens safety, but should be used at the lowest effective dose and for the shortest duration possible due to potential side effects (e.g., extrapyramidal symptoms, cardiac arrhythmias) 1 15 16 17 19.

Other Medications

• Dexmedetomidine: An alpha-2 agonist, dexmedetomidine may reduce delirium duration and facilitate earlier extubation in ICU patients, but evidence is limited and potential side effects require close monitoring 19.
• Ramelteon and Melatonin: Some studies suggest these agents may help prevent delirium, particularly in high-risk patients, but more research is needed 18.
• Combination Therapy: Haloperidol plus lorazepam may be more effective than placebo in some cases, but risks must be weighed carefully 18.

Prevention

Prevention strategies are highly effective and include:

• Early mobilization and physical therapy
• Avoiding or minimizing deliriogenic medications
• Sleep promotion protocols and minimizing nighttime noise/light
• Maintaining orientation cues and regular routines
• Ensuring hearing aids/glasses are available for those with sensory impairments

These approaches have been shown to reduce the incidence and duration of delirium across hospital settings 13 1 18.

Conclusion

Delirium is a complex, multifaceted syndrome with far-reaching consequences for patients and healthcare systems. Early recognition, prevention, and comprehensive management are key to improving outcomes.

Key Takeaways:

• Symptoms: Core features are acute inattention, disorientation, disturbed consciousness, and fluctuating cognition. Symptoms vary by age and may include psychomotor and perceptual changes 1 3 4.
• Types: Delirium is classified into hyperactive, hypoactive, mixed, and subsyndromal forms—each with distinct clinical implications and prognoses 6 9 10.
• Causes: It arises from a combination of predisposing vulnerabilities and acute precipitating factors, with neurochemical and inflammatory changes at its core 1 11 12 14.
• Treatment: Non-pharmacological, multifactorial strategies are most effective. Medication review is vital; antipsychotics have limited roles and should be used cautiously. Prevention remains the best therapy 1 14 15 16 19.

Understanding delirium’s symptoms, types, causes, and treatments empowers clinicians, patients, and families to advocate for evidence-based care and improved outcomes.