“Healthy people differ significantly in their overall personality, mood, and behavior. Each person also varies from day to day, depending on the circumstances. However, a sudden, major change in personality and/or behavior, particularly one that is not related to an obvious event (such as taking a medication or losing a loved one), raises concern for a mental health issue.

Sudden changes in personality and behavior can be roughly categorized as involving one of the following types of symptoms:

• Confusion or delirium

• Delusions

• Disorganized speech or behavior

• Hallucinations

• Mood extremes (such as depression or mania)

These categories are not specific mental illnesses. They are just one way doctors organize different types of abnormal thought, speech, and behavior. These changes in personality and behavior can be caused by general medical conditions or mental health issues.”

MERCK MANUAL (Personality and Behavior Changes – Mental Health Disorders – Merck Manual Consumer Version)