Glioblastoma changes how the brain processes thought and who a person seems to be. Aggression, apathy, and impulsivity are among the most distressing symptoms caregivers encounter yet rarely discussed in clinical visits. Understanding what drives these changes is the first step toward managing them.
What Causes Personality Changes in Glioblastoma?
Personality and behavioral changes in glioblastoma result from the tumor disrupting brain circuits that regulate emotion, impulse control, and social behavior. The tumor can compress or invade these circuits. Swelling from the tumor or treatment adds pressure. Drugs used to treat glioblastoma, particularly corticosteroids, can also change mood and behavior. The American Brain Tumor Association describes these as neuropsychiatric symptoms - mood, cognitive, and behavioral changes that come from the tumor, its treatment, or both.
If you are a caregiver watching someone become irritable, withdrawn, or impulsive, that experience is real. The changes are not a choice. They are a neurological result of where the tumor is growing and what it is damaging.
How Tumor Location Shapes the Changes You See
Glioblastoma most often grows in the frontal and temporal lobes. These regions control personality, emotional regulation, and social judgment. The changes a person shows depend closely on which circuits the tumor is pressing on or damaging.
Frontal Lobe Tumors
The frontal lobe controls planning, impulse control, empathy, and decision-making. A tumor here can produce three patterns. A lesion in the orbitofrontal area - the lower front of the brain, behind the eye socket - often leads to poor judgment, impulsivity, and social disinhibition. A tumor in the dorsolateral prefrontal area can damage planning and executive function. Damage to medial frontal areas is more likely to cause apathy or abulia - a loss of drive to start or finish activities. A systematic review in Neuro-Oncology Practice found that tumors in the frontal lobe are linked to high rates of personality and behavioral change in glioma patients.
Temporal Lobe Tumors
The temporal lobe is involved in emotional memory, language, and social processing. Tumors here tend to produce emotional swings, irritability, and sometimes paranoid thinking. Because the temporal lobe connects to the limbic system - the brain's emotional center - temporal tumors can trigger sudden anger, fear, and dramatic mood shifts that feel out of proportion to what caused them.
Deep and Limbic Involvement
Some glioblastomas extend into limbic structures like the cingulate cortex and amygdala. These areas control emotional regulation. When they are damaged, caregivers may see a person swing rapidly between calm and agitation, or react strongly to small frustrations. In some cases, psychiatric symptoms like these are the first sign that a tumor is growing - before a formal diagnosis is made. Research on psychiatric symptoms in glioma patients confirms that subtle neuropsychiatric changes can appear weeks or months before a GBM diagnosis is confirmed on imaging.
When Treatment Is the Driver
Not every behavioral change in glioblastoma comes from the tumor directly. Treatment can cause its own neuropsychiatric effects, and telling tumor-driven changes from treatment-driven changes matters - because the management approach differs.
Corticosteroids
Dexamethasone is used during GBM treatment to control brain swelling. It works well and is often necessary. But corticosteroids are one of the most common causes of drug-induced behavioral change in this disease. Side effects can include irritability, mood swings, insomnia, mania, and - less commonly - steroid psychosis, a state of confusion, agitation, or hallucinations. These effects tend to be dose-dependent, meaning higher doses carry greater risk. If you have noticed a sharp personality shift after a steroid dose increase, that connection is worth raising with the care team. For a detailed look at steroid effects during GBM treatment, the article on dexamethasone side effects and tapering covers the full picture, including safe tapering strategies.
Chemotherapy and Radiation
Temozolomide and radiation both affect the brain, and treatment fatigue can deepen apathy that already exists. Chemo brain refers to a cluster of cognitive and mood effects that include slowed thinking, emotional flatness, and difficulty concentrating. These overlap with apathy caused by the tumor, which makes the two hard to separate. A review on brain tumor emotional and behavioral functioning notes that mood and behavioral symptoms in GBM patients often come from multiple sources - the tumor, treatment, and the stress of diagnosis at the same time. For more on the cognitive side of these changes, the article on cognitive changes during glioblastoma treatment covers memory, brain fog, and concentration in depth.
Aggression, Apathy, and Impulsivity: What Each One Looks Like
These three changes are most commonly reported by caregivers - and they often get confused with one another or with depression. Understanding the difference helps caregivers respond better and explain symptoms accurately to the medical team.
Aggression
Aggression in GBM patients most often takes a verbal form: raised voices, accusations, and hostile comments that feel unprovoked. Physical aggression is less common but does occur, especially when a patient is confused or scared. The aggression usually does not reflect genuine hostility. It reflects a brain that has lost the circuits that normally control frustration. Triggers are often minor - a change in routine, a perceived slight, or a task the patient can no longer complete. Recognizing that the aggression is neurological rather than personal matters for caregivers, even when it hurts in the moment. If aggressive behavior is escalating or putting someone at risk, that is an urgent conversation for the oncology team and possibly a neuropsychiatrist.
Apathy
Apathy is not the same as depression, though they can overlap. A person with apathy loses motivation and drive. They may stop starting conversations, show no interest in activities they once valued, or need constant reminders to complete daily tasks. Importantly, they often do not feel sad about this. They feel flat instead of distressed. A scoping review published in Neuro-Oncology Practice identified apathy and loss of drive as among the most difficult behavioral changes for family caregivers - partly because it can look like withdrawal from life, when it is actually a neurological symptom. Distinguishing apathy from depression matters because the treatments differ, and antidepressants often do not help apathy.
Impulsivity
Impulsivity appears as poor judgment, reckless decisions, disinhibition, or behavior that seems socially out of place. A patient may make financial decisions without consulting anyone. They may say things in public that would normally be filtered. They may act on urges without thinking about consequences. This typically points to orbitofrontal damage - disruption of the circuits that regulate social behavior and restraint. Caregivers dealing with impulsivity may need practical safeguards like limiting access to financial accounts or gently redirecting social interactions, alongside medical evaluation.
The Caregiver Experience
Watching someone's personality change is a particular kind of grief. The person is still there physically, but their humor, patience, and warmth may have shifted or disappeared. Caregivers managing aggression or impulsivity at home face high burnout risk. Sleep disruption is common when a patient is agitated at night or needs close watching. If that is your situation, talk to the care team about options that might help.
Behavioral changes in GBM are often not explained well to families at diagnosis. Caregivers frequently spend weeks seeing these behaviors as intentional or as a sign of depression before making a neuropsychiatric connection. Naming what is happening - as a symptom, not a choice - can reduce conflict and help families work better with the clinical team.
If you are unsure whether what you are seeing reflects tumor growth, treatment side effects, or a manageable neuropsychiatric condition, getting a second opinion is a good idea. You can upload your MRI scans and clinical reports to the Glioblastoma Center patient journey team for a remote review that places behavioral symptoms in the full clinical picture.
What Can Help
Behavioral and personality changes in GBM are manageable to varying degrees, depending on their cause. The first step is an accurate assessment by a neuropsychiatrist or a neurologist with brain tumor experience - someone who can tell tumor effects from treatment effects from psychological reaction.
Pharmacological options exist for specific symptoms. Severe impulsivity and mood swings may respond to mood stabilizers or anticonvulsants - the oncology team can discuss what is appropriate for each case. Apathy sometimes improves when steroid doses go down. Steroid-induced psychiatric symptoms typically improve by adjusting the dexamethasone dose where safe. Any medication change should involve the full oncology team, since interactions with anti-seizure drugs, chemotherapy, and corticosteroids are common.
Psychosocial interventions also help. Problem-solving therapy, caregiver education programs, and behavioral management strategies have been studied in patients with brain tumors. Consistent routines, calm environments, and clear communication may reduce how often and how intense behavioral episodes are at home.
Seizures are another factor worth checking. Behavioral disturbances in GBM patients can sometimes come after a seizure that may not have been noticed. The article on seizures in glioblastoma covers signs, triggers, and anti-seizure medication and is a useful parallel read for caregivers dealing with both issues.
When to Talk to Your Doctor
Raise behavioral changes with the oncology or neurology team if: the changes appeared or worsened after a medication change; the patient is showing confusion or disorientation with behavioral shifts; aggression or impulsivity is putting the patient or others at risk; or the changes are making it hard to attend or complete treatment. A neuropsychiatric referral is a legitimate and valuable part of GBM care - not a secondary concern.
This article is for general information and is not a substitute for medical advice. Always consult your oncologist or care team about your specific situation.