Yes, chemotherapy (chemo) can cause personality changes, often linked to "chemo brain" affecting thinking, mood swings, irritability, depression, anxiety, or confusion, stemming from treatment's direct effect on the brain, stress, and emotional toll of cancer itself, leading to shifts in behavior and self-perception. These cognitive and emotional impacts are common and can range from mild to significant, affecting concentration, memory, and emotional regulation, notes Healthline, Cleveland Clinic, National Cancer Institute, and CancerCare.
Some people with cancer notice that they can't think as clearly as they used to. They may have trouble remembering things, focusing, finishing tasks, or learning something new. These are symptoms of cognitive impairment, also known as “chemo brain” or “brain fog.”
Depression and anxiety in cancer survivors
Lingering feelings of sadness and anger can interfere with your daily life. For many people, these feelings become less intense with time. But for others, these feelings can develop into depression. Tell your provider about your feelings.
The physical side effects of cancer can affect your emotions. Often if our body doesn't feel good, we don't feel good mentally either. For example, if someone is in pain, they might get cranky with others. Or if people are fatigued, it might make them feel sad.
Frontal lobe brain tumors might cause balance problems and trouble walking. There might be personality changes, such as forgetfulness and lack of interest in usual activities.
They might become very sleepy and out of touch with what's going on around them. Or they might start to act very upset and nervous. Most often, the person will not be aware of these changes, but their family members or cancer care team will notice them.
Causes of Personality and Behavior Changes
Can chemo brain affect personality? Some studies suggest chemo brain can contribute to depression, frustration or irritability. This can make everyday tasks feel harder than they used to. It's normal to feel discouraged, but recognizing these changes can help you find effective coping strategies.
The 62-day rule for cancer, primarily in the UK's NHS system, is a key waiting time target: patients who receive an urgent referral for suspected cancer should begin their first cancer treatment within 62 days from the date the hospital gets that referral. It's part of broader standards that also include a 28-day "Faster Diagnosis" goal (diagnosis or ruling out cancer within 28 days of urgent referral) and a 31-day "Decision to Treat" standard (treatment within 31 days of the agreed-upon plan).
While some studies suggest a link between chemotherapy and mild cognitive impairment, which is considered a precursor to dementia, the evidence is somewhat limited. Some data suggests chemotherapy may not increase the risk of developing dementia.
England. NHS England has introduced a new target called the Faster Diagnosis Standard (FDS). The target is that you should not wait more than 28 days from referral to finding out whether you have cancer or not. The FDS applies to anyone with a suspected cancer, even if you have been treated for cancer in the past.
Worry, anxiety and loneliness: 72% of people living with cancer have emotional concerns like anxiety or depression - rising to 84% for those with a disability.
You might have physical changes like hair loss, skin changes or new scars, ostomies, weight changes, or loss of limbs. Cancer and treatment might also cause changes to your sex organs, sexual health, fertility, or mental health. Some of the changes may be temporary, while others are permanent.
Chemotherapy regimens have been associated with multiple psychiatric complications, including psychosis, mania and anxiety. Capecitabine is implicated to be associated with encephalopathy whose clinical presentation often mimics that of psychosis.
The term “chemo brain” was coined to describe mild cognitive problems in cancer patients attributed to chemotherapy. Although minor chemotherapy-induced memory and cognitive impairments have been described previously, a case-cohort study suggests that these effects can persist more than 20 years posttherapy.
About 90% of cancers are caused by environmental and lifestyle factors, not genetics, including smoking, poor diet (red meat, fried foods), alcohol, sun exposure, pollutants, infections, obesity, and inactivity; only 5–10% are due to inherited genetic defects, with most cancers arising from lifestyle-induced genetic mutations. Tobacco alone accounts for about a third of cancer deaths, while diet, obesity, and inactivity contribute significantly, with controllable factors being key to prevention.
Sometimes described as the “3-2-1-0 rule”, the original Amsterdam criteria defined HNPCC (as it was known at the time) by 3 or more individuals with pathologically confirmed colorectal cancer where one affected family member is a first-degree relative of the other 2, in at least 2 successive generations, with one ...
When is it time to think about stopping cancer treatment? If you have had three different treatments and your cancer has grown or spread, more treatment usually will not help you feel better or increase your chance of living longer.
Chemo brain
Emotional and mental health challenges such as depression, anxiety, stress, and having trouble sleeping can add to that foggy feeling. Chemo brain can also intensify feelings of frustration or anger. That's OK. These feelings can be managed.
Psychosis or mania as an adverse effect of chemotherapy are rare and uncommon. To date there has been only two other reports of capecitabine and oxaliplatin causing mania like symptoms (Garg et al., 2018; Kaur et al., 2022).
Anxiety, panic, depression, post-traumatic stress disorder (PTSD), bipolar disorder, schizophrenia, and others can all fundamentally change how a person perceives and interacts with the world around them. Lastly, addiction can play a large role in these sudden personality changes.
The first stage of a mental breakdown, often starting subtly, involves feeling overwhelmed, exhausted, and increasingly anxious or irritable, coupled with difficulty concentrating, changes in sleep/appetite, and withdrawing from activities or people that once brought joy, all stemming from intense stress that becomes too much to handle.
Personality disorders involve pervasive patterns of distorted thinking, feeling, and behaving, leading to significant distress and functional problems, often seen as intense mood swings, unstable relationships, difficulty with self-image, impulsive/risky actions, extreme suspicion, emotional detachment or drama, difficulty controlling anger, sensitivity to criticism, trouble with boundaries, and issues with empathy or morality. These signs manifest differently across the various types, such as Borderline, Narcissistic, or Avoidant Personality Disorders, but generally impact how a person sees themselves, interacts with others, and manages emotions.