Personality and Mood Changes

Why dementia can change a person's mood and personality—from apathy and irritability to anxiety, suspicion and loss of inhibitions—and practical, compassionate ways families can respond.

Last reviewed: October 2026

"He's just not himself anymore." Many families say this long before anyone mentions a diagnosis. Memory loss gets most of the attention, but dementia can also change how a person feels, reacts and relates to others. A gentle father may become short-tempered. A lively, social mother may stop calling friends. These changes can hurt, but understanding them makes them easier to handle.

The most important thing to remember, as the National Institute on Aging (NIA) puts it: the disease, not the person, causes these changes.

Why personality and mood change

Dementia damages brain cells in areas that control emotion, judgment and self-control—not just memory. Mayo Clinic explains that the brain changes of Alzheimer's Disease can affect moods and behaviors. NIA also notes that the person might seem like themselves one day and act in unusual ways the next, and that this day-to-day variation is common.

Other things can trigger or worsen behavior changes, according to NIA:

Emotions such as sadness, fear, stress, confusion or anxiety
Health problems, such as pain, poor sleep, or trouble seeing or hearing
Physical needs like constipation, hunger or thirst
Side effects of new medicines—see Medications That Can Affect Memory
A noisy or stressful setting, such as several conversations at once or a loud TV

Common changes

Mayo Clinic and NIA describe a range of mood and personality changes, including:

Depression and low mood
Apathy—loss of interest in activities, hobbies or people
Social withdrawal
Mood swings, and getting upset, worried or angry more easily
Anxiety or fear
Suspicion and distrust, including believing others are hiding or stealing things
Loss of inhibitions—saying or doing things that seem rude or out of character
Anger or aggression—see Agitation and Aggression
Changes in sleep—see Sleep Problems in Dementia

Some people also see or believe things that aren't real; see Hallucinations and Delusions.

When personality changes come first

In most Alzheimer's disease, memory problems come first and mood changes follow. But in frontotemporal dementia (FTD), personality and behavior changes are often the earliest and most striking signs. NIA describes behavioral variant FTD—the most common type—as causing changes in personality, behavior and judgment. People may act impulsively, lose interest in family, seem to lack empathy, or behave inappropriately in public, often without realizing it. Memory may be fine at first.

NIA notes that FTD tends to begin at a younger age than other dementias—roughly 60% of people with FTD are 45 to 64 years old. Because of that, early changes can be put down to stress or other life problems rather than a brain disease. See Frontotemporal Dementia and Young-Onset Dementia.

Depression or dementia—or both?

Depression is common in dementia. The Alzheimer's Association says experts estimate that up to 40 percent of people with Alzheimer's or another dementia may have significant depression, especially in the early and middle stages.

It can be hard to spot, because dementia and depression share symptoms—losing interest in activities, withdrawing, trouble concentrating. The Association notes that depression in dementia may be milder, come and go, and show up as physical complaints such as pain or fatigue. People in later stages may not be able to put sadness into words.

The good news: depression is treatable, and treatment can improve quality of life. Treatment usually combines counseling or support groups, gentle reconnection with enjoyable activities and people, and sometimes medicine. Telling someone to "cheer up" or "try harder" rarely helps, the Association adds. See Depression and Memory ("Pseudodementia").

How to respond

These approaches, drawn from NIA and the Alzheimer's Association, help many families:

Don't take it personally. Hurtful words or coldness come from the illness.
Stay calm and avoid arguing. Correcting or reasoning often makes things worse. Reassure the person that you're there to help.
Look for a trigger. Is the person in pain, tired, hungry, overstimulated, or reacting to a new medicine? Keeping a simple log of when changes happen can reveal a pattern.
Redirect. Shift attention to music, a walk, a snack, looking at photos or a simple task.
Keep a steady routine. Bathing, dressing and meals at the same times each day reduce stress.
Simplify the setting. Reduce noise and clutter; keep familiar, well-loved objects nearby.
Encourage activity. Physical activity can improve mood and sleep, per NIA.
Plan around the best time of day for harder tasks like bathing.
Offer reassurance and connection. Let the person know they are loved and still part of the family, and find small ways for them to contribute.

For more on talking with someone whose thinking has changed, see Communicating with Someone with Dementia. For when behavior is harder to manage, see Managing Challenging Behaviors and Treating Behavioral Symptoms.

Look after yourself, too

Watching someone's personality change is a kind of grief, even while they are still here. It's normal to feel sad, frustrated or even angry. Support groups, respite care and honest talks with family can help. See Caregiver Stress and Burnout and Grief and Ambiguous Loss.

When to see a doctor

Talk with the person's doctor if you notice:

New or worsening mood or personality changes
Signs of depression lasting more than a couple of weeks
Suspicion, aggression or disinhibition that puts anyone at risk
Personality changes in someone under 65, or without memory loss

NIA advises that sudden or rapidly changing behavior—especially after an infection or a medicine change—should be brought to a doctor's attention right away. A sudden change can signal delirium, a urinary tract infection or another treatable problem; see Delirium vs. Dementia.

If anyone talks about suicide or is in danger, call or text 988 (Suicide & Crisis Lifeline) or 911. The Alzheimer's Association's 24/7 Helpline is 800-272-3900. This article is general information; please talk with a doctor about the specific changes you're seeing.

Sources

Not medical advice. This article is general information, not a diagnosis or treatment plan for any individual. Talk with a doctor about your situation.

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We may answer common questions in future updates (we won't share your name). We can't give personal medical advice; for urgent help call the Alzheimer's Association Helpline at 800-272-3900.

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