Sudden personality changes that have no cause
It can be very difficult to see a child experience extreme personality changes that do not seem to have an origin, because you want to feel like you know and understand them. Of course, moods can vary, so slight alterations to one's personality can occasionally be normal. However, a significant personality change usually falls under one of the following categories: confusion, delusions, disorganized speech or behavior, hallucinations, and extreme moods. If you observe any of these in your child, it is important to seek help for them, which begins at the doctor.
The causes of such changes in personality are often mental disorders such as bipolar disorder, schizophrenia, depression, or sometimes even posttraumatic stress disorder; bear in mind that your child could be struggling with such a condition without you even knowing about the trauma that had occurred. If your child ever becomes violent, a doctor should be contacted immediately.