How to tell if someone is having mental health issues

Schizophrenia is characterised by delusions, hallucinations, and disorganised thinking and speech. — TNS

I recently noticed my colleague’s change in behaviour over the past year. For the last nine years that I have known her, she was a happy and well-adjusted person whom the other team members looked up to as ‘big sister’. People went to her for advice. But this year, she has been having bizarre and erratic behaviour swings. What is strange is that when she is unhappy, she will tell you that she is sad, but she will be wearing a happy smile. I find this very odd, especially when she has never been like this in the past.

There are many causes for a sudden or gradual change in behaviour in a person you know well.