If a doctor thinks someone may have schizophrenia, they will interview that person, as well as their friends and family members.
Psychiatrists have the most experience with this.
To make the diagnosis, all of these things must be true about a person:
They’ve had schizophrenia symptoms for at least 6 months.
The symptoms cause major problems, such as trouble with work or relationships.
There’s no other likely diagnosis, such as drug use or a different mental illness.