The early stages of a mental disorder were beginning to show in the patient.
Mentally disturbed - A very small group of people have a mental disorder which compels them to steal.
If your loved one doesn't have a mental disorder and you don't believe it's part of his/her personality, it could very well be a learned response.
Autism is a profound mental disorder marked by an inability to communicate and interact with others.
The Diagnostic and Statistical Manual of Mental Disorders (DSM) does not recognize lying as a mental disorder.