The short answer
Brain tumors can bring changes in personality, mood, focus and behavior. Medicines such as steroids can also affect mood. This page covers daily strategies, urgent signs, and support for carers.
NCI lists changes in personality, mood, focus or behavior among the symptoms of a brain tumor.
Medicines such as dexamethasone can affect mood and sleep, so ask the team to review the medicine list before assuming the tumor has grown.
A sudden change over hours or days is not a personality issue and needs an urgent call or emergency care.
A seizure that lasts longer than 5 minutes, repeated seizures, or a first-ever seizure means call 911.
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This page is for families of someone whose personality, memory or behavior has changed because of a brain tumor. It covers possible causes, what can help day to day, and when to get help fast.
What families notice first
NCI lists "changes in personality, mood, ability to focus, or behavior" among the symptoms of a brain tumor. Families may see someone who is quieter, more irritable, or less like themselves.
Two things are worth saying plainly. These changes are a symptom of the illness or its treatment. They are not a choice. And the person may not notice the change themselves, so arguing about it rarely helps.
Medicines can play a part
Do not assume the tumor has grown before the team has reviewed the medicine list.
- Steroids such as dexamethasone are used in brain tumor care. MedlinePlus lists insomnia, restlessness, depression and anxiety as possible side effects. It also says that stopping the drug suddenly can cause confusion, so doctors lower the dose gradually. Never stop it on your own.
- Other medicines can also affect mood or thinking. Ask the team to review everything the person takes, including medicines for seizures or pain.
Write down the dates of any dose change. It helps the team see patterns.
A sudden change over hours or days is not a personality issue. See When to get help sooner below.
What helps day to day
- Keep a diary. Note the date, the time, what happened, and what the person had taken. Share it with the team.
- Keep things simple. Give one instruction at a time. Use short sentences and a steady daily routine.
- Use memory aids. NCI suggests planners, written lists and recorders, and doing the tasks that need the most focus at the time of day the person feels best.
- Talk about the behavior, not the person. "That is not okay to say here" is calmer than "why would you say that?"
- Safety. Ask the team about driving rules after a brain tumor diagnosis or a seizure. Plan ahead for what you would do if someone became aggressive, including who to call.
- Ask about specialists. NCI suggests asking whether a neuropsychologist or an occupational therapist could help.
Looking after the carer
Caring for someone whose personality has changed is hard. NCI says caregiver stress can bring tiredness, sleep problems, anxiety and depression. Feeling anger, sadness or guilt is common.
NCI suggests talking with a counselor, such as a social worker, psychologist or faith leader. Support groups, in person, by phone or online, are another option. A hospital social worker can also point you to local help. Ask for support for yourself, not only for the patient.
When to get help sooner
Slow drift is something to manage with the team. A change that arrives over hours or a day or two is a medical event, and the tips on this page are the wrong tool for it.
- Call 911 or go to an emergency department if a seizure lasts longer than 5 minutes, one seizure follows another soon after, or the person has never had a seizure before. CDC lists all three as reasons to call 911. Do the same for trouble breathing, difficulty waking up, or an injury during a seizure. Also call 911 for a sudden drop in alertness, new weakness on one side, or a sudden change in speech.
- Call 911 or go to an emergency department if confusion comes on over hours, the person no longer knows where they are or what time it is, or they are much harder to wake than yesterday. Do the same for a sudden severe headache, or a headache with repeated vomiting. These need to be checked in person, not by phone.
- Call the team the same day if the person starts seeing or hearing things that are not there, a headache is worse in the morning or when lying flat, or aggression has become unsafe for them or for you. If anyone is in immediate danger, call 911.
- Call the team within a day or two if irritability, low mood, sleeplessness or agitation started or got worse after a steroid dose change or a new medicine. Bring the diary and the dates.
Sources
Opened and checked on 2026-10-02:
Common questions
Is this the tumor or the medication?
It can be either, or both. NCI lists personality, mood and behavior changes as brain tumor symptoms. MedlinePlus says dexamethasone, a steroid, can cause insomnia, restlessness, depression and anxiety. Ask the team to go through the medicine list and the dates of any dose changes. Do not stop or change a medicine on your own.
When is a change urgent rather than gradual?
A sudden change over hours or days, such as new confusion, not knowing where they are, seeing things that are not there, being very hard to wake, or a first seizure, needs urgent care. Call 911 or go to an emergency department for a seizure, a sharp drop in alertness, new weakness on one side or a sudden change in speech. For slower changes, call the team within a day or two.
What help can we ask for?
NCI suggests asking whether specialists such as a neuropsychologist or an occupational therapist could help with memory and thinking problems. Ask the team what else is available for your situation.
Is it normal to feel stressed, angry or sad as a carer?
Yes. NCI says caregiving can have physical and emotional effects, including tiredness, sleep problems, anxiety and depression. It suggests talking with a counselor, such as a social worker, and joining a support group. Ask your own doctor or the oncology social worker for help.
Questions to ask your doctor
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Get urgent help
Fever of 100.4°F (38°C) or higher during chemo, severe pain, or trouble breathing: call your cancer care team right away, day or night. Call 911 for an emergency.
Where to get help with this, by name
A hospital social worker or financial navigator is the best first call if you have one. If you do not, these organisations help at no cost to you.
- Patient Advocate Foundation — (800) 532-5274. Case managers take on insurance appeals, denials and medical debt with you. Free.
- TotalAssist (Patient Advocate Foundation's copay programme, merged with the PAN Foundation in 2026) — 866-512-3861. Help with medication copays, coinsurance and deductibles, insurance premiums, and office-visit and administration charges on the day of treatment, across nearly 150 conditions.
- CancerCare — 800-813-HOPE (4673). Oncology social workers, free counselling and support groups. Limited financial help with transport, home care, child care and lodging for people in active treatment who meet their income guidelines — funding is first-come, first-served, so call to ask what is open.
- Triage Cancer — 424-258-4628. Free legal and financial navigation: insurance, employment rights, disability.
- Blood Cancer United (formerly the Leukemia & Lymphoma Society) — (800) 955-4572. Information Specialists answer questions on treatment, insurance and financial problems.
- HealthCare.gov — 1-800-318-2596. For questions about the external review process — the independent review your insurer is required by law to accept.
Your state Department of Insurance regulates insurers and takes consumer complaints. On Medicare, your State Health Insurance Assistance Program (SHIP) gives free one-to-one counselling. If a specific drug is the problem, ask the manufacturer about its patient assistance programme.
Phone numbers checked 31 July 2026. Programmes and eligibility change — if a number has moved, please tell us.
Plain-language explanation of the published sources cited on this page. AI-assisted, source-checked, not clinician-reviewed.
Written by: Cancer ExplainedSources last checked: 2026-10-02 what this meansLast updated: 2026-10-02Next planned review: 2028-07-30
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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