Adolescents between the ages of 16-25 are a very different population then an older generation of people with a long history of schizophrenia, although the females tend to be older at the first episode than the males. In London they don't stress a diagnosis of schizophrenia or bipolar disorder to the patient. Adolescents can accept a psychotic episode easier than a permanent disabling disease. If they follow the treatment they can be prevented. Only half of the patients in the London program have ever been hospitalized in a psychiatric hospital.
Referrals come from a variety of sources.
A diagnosis of psychosis doesn't depend on an involuntary admission to a hospital which means that the patient is a danger to themselves or others. I came across this term first reading up on ACT teams that have become popular of late. One team in Toronto focused on the homeless mentally ill. Workers have to approach these people to help them obtain housing and convince them to take medication. It can take many, many months.