A woman who was gentle her entire life begins shouting at her daughter. A retired teacher accuses his wife of stealing from him. Someone who has never been anxious paces the hallway for hours, unable to settle. A father who was reserved and private starts saying things in public that would have mortified him a decade earlier.
For families, these changes are often more distressing than the memory loss. Forgetting is expected. Personality change feels like something else entirely, like the person is being replaced by someone else. Families frequently describe feeling that the behavior is directed at them, that their loved one is being deliberately difficult, or that something has gone wrong beyond the disease itself.
The clinical literature calls these behavioral and psychological symptoms of dementia, abbreviated as BPSD. Understanding what they are and what causes them changes how families experience them and how effectively they can be managed.
How Common Are They
BPSD are not an unusual complication. They are a core feature of the disease. Research indicates that up to 90% of people with dementia experience some form of behavioral or psychological symptom over the course of the illness. A 2025 systematic review and meta-analysis published in Age and Ageing examining BPSD in hospital settings found that 60% of older hospital patients with dementia had one or more BPSD symptoms, including aggression, sleep disturbance, eating problems, and irritability.
These symptoms significantly affect prognosis, quality of life, and caregiver burden. They are also, importantly, among the most treatable aspects of dementia. Unlike the underlying cognitive decline, which cannot currently be reversed, behavioral symptoms often respond meaningfully to intervention.
The Five Categories
Clinicians typically group BPSD into five domains, which helps organize what can otherwise feel like a chaotic set of changes.
Cognitive and perceptual symptoms include delusions and hallucinations. Delusions in dementia commonly involve theft, infidelity, or the belief that people in the home are strangers or impostors. Hallucinations, particularly detailed visual hallucinations, are especially common in Lewy body dementia.
Motor symptoms include pacing, wandering, repetitive movements, and physical aggression.
Verbal symptoms include yelling, calling out repeatedly, repetitive questioning, and verbal aggression.
Emotional symptoms include depression, apathy, anxiety, irritability, and occasionally euphoria.
Vegetative symptoms involve disturbances in sleep and appetite.
Most people with dementia experience symptoms across several of these domains, and the specific pattern often shifts as the disease progresses.
Why These Behaviors Happen
This is the part that changes how families understand what they are seeing.
The brain regions that regulate behavior are being damaged. Agitation, disinhibition, and psychosis in dementia are associated with measurable volume reduction and decreased metabolism in specific brain regions, including the dorsolateral prefrontal cortex, orbital prefrontal cortex, anterior cingulate, insula, and temporal lobes. These are precisely the areas responsible for emotional regulation, self-awareness, impulse control, and accurate perception. Apathy, by contrast, is more associated with small vessel white matter disease.
This means that when someone with dementia becomes aggressive or says something inappropriate, the neurological system that would normally inhibit that response has been physically damaged. The behavior is not a choice, and it is not a reflection of who the person really is underneath. It is a symptom, in the same way that memory loss is a symptom.
Unmet needs the person cannot communicate. A large proportion of behavioral symptoms are driven by needs the person cannot articulate. Pain is the most commonly missed. Someone with arthritis, a urinary tract infection, dental pain, or constipation may become agitated or aggressive because they are hurting and cannot say so. Hunger, thirst, needing a bathroom, being too hot or cold, and fatigue all produce the same pattern.
Environmental triggers. Noise, crowding, unfamiliar surroundings, too much stimulation, or too little all contribute to behavioral symptoms. The 2025 hospital-based meta-analysis specifically found that BPSD were linked to uncomfortable interventions, poor patient-staff interactions, and the disorienting nature of the hospital environment itself.
Delirium. Acute confusion superimposed on dementia, usually caused by infection, medication changes, dehydration, or hospitalization, produces sudden behavioral changes. A rapid onset of new agitation or confusion in someone with dementia should always prompt evaluation for delirium, because the underlying cause is often treatable.
Medications. Certain drugs, particularly anticholinergics, some sedatives, and occasionally the medications used to treat behavioral symptoms themselves, can worsen confusion and agitation. Medication review is a standard part of BPSD assessment for this reason.
Fear and loss of control. Beneath many behaviors is a person who does not know where they are, does not recognize the people around them, and cannot understand what is being asked of them. Resistance to bathing, for example, often reflects a person who does not understand why a stranger is removing their clothes. Reframed that way, the behavior makes sense.
What the Guidelines Say About Management
A 2024 systematic review published in the Journal of the American Medical Directors Association synthesized recommendations across moderate to high quality clinical practice guidelines on dementia care. The consistent recommendation across guidelines is that non-pharmacological approaches should be first-line, with medication reserved for situations involving serious risk or where non-drug approaches have failed.
Identify and address the trigger. The first clinical step is always to look for a cause. Assess for pain, infection, constipation, dehydration, medication effects, and environmental stressors before assuming the behavior is simply part of the disease. A meaningful proportion of behavioral symptoms resolve when the underlying cause is treated.
Adjust the environment. Reducing noise, simplifying visual clutter, improving lighting, maintaining consistent routines, and limiting the number of unfamiliar people all reduce behavioral symptoms. As covered in the boutique care post in this series, environmental factors have measurable effects on the frequency and severity of neuropsychiatric symptoms.
Change the approach, not the person. Slowing down, using simple language, approaching from the front rather than from behind, explaining what is about to happen before doing it, and offering choices where possible all reduce resistance and agitation during care tasks.
Do not argue with delusions. Correcting a delusion rarely resolves it and usually escalates distress. If a person believes someone is stealing from them, arguing about the facts is less effective than acknowledging the feeling, redirecting attention, and, practically, keeping duplicates of commonly misplaced items.
Use structured activity and engagement. Music, physical activity, familiar tasks, and social engagement all reduce behavioral symptoms. The evidence base for music specifically, covered in a separate post in this series, is among the strongest.
Medication with caution. Antipsychotics are sometimes appropriate for severe agitation or psychosis that poses a genuine risk, but they carry significant risks in older adults with dementia, including increased mortality, stroke, falls, and accelerated cognitive decline. Clinical guidelines uniformly recommend using the lowest effective dose for the shortest necessary duration, with regular reassessment for whether the medication can be reduced or stopped. Antidepressants may be appropriate for depression and, in some cases, for agitation.
What Families Should Take From This
The single most useful reframe is this: behavior in dementia is communication. When someone with dementia cannot tell you they are in pain, frightened, exhausted, or overwhelmed, the message comes out as behavior instead. The clinical approach to BPSD is essentially an exercise in translation, working backward from the behavior to figure out what it is expressing.
That reframe also relieves something families carry unnecessarily. If a parent becomes hostile or accusatory, it is not a statement about the relationship, about whether they love you, or about whether you are doing enough. It is a symptom of damage to the specific parts of the brain that regulate those responses.
If behavioral symptoms are escalating or becoming unmanageable, that is worth raising specifically with the person’s physician rather than treating as an inevitable part of the disease. Many of these symptoms respond to intervention, and a systematic evaluation for treatable causes is warranted whenever behavior changes noticeably.
Many behavioral symptoms in dementia share underlying causes with wandering. Our post on wandering covers why that behavior occurs, what drives it, and what the research says reduces the risk, including several of the same environmental and needs-based approaches described here.
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Sources
- Tible OP, et al. Behavioral and Psychological Symptoms in Dementia. StatPearls. NCBI Bookshelf. Updated 2024.
- Watt JA, et al. Guideline Recommendations on Behavioral and Psychological Symptoms of Dementia: A Systematic Review. Journal of the American Medical Directors Association. 2024;25(5):837-846.
- Zhang Y, et al. Behavioural and psychological symptoms of people with dementia in acute hospital settings: a systematic review and meta-analysis. Age and Ageing. 2025;54(1).
- Watt JA, et al. Comparative efficacy of interventions for aggressive and agitated behaviors in dementia: a systematic review and network meta-analysis. Annals of Internal Medicine. 2019;171(9):633-642.
- Cerejeira J, Lagarto L, Mukaetova-Ladinska EB. Behavioral and psychological symptoms of dementia. Frontiers in Neurology. 2012;3:73.
- Alzheimer’s Association. 2025 Alzheimer’s Disease Facts and Figures. Alzheimer’s & Dementia. 2025.