Dr. Davidson stated that he had to modify his presentation due to changes in some data. He decided to talk about the difficulties with defining the first episode of psychosis.

The question of first episode of psychosis may actually be one of several questions. For example, "When does the first symptom of psychosis manifest itself? When does someone ask for help? When is someone finally diagnosed as psychotic?"

It is important not to confuse the answers to each of these questions because they are quite different. It is much harder to discover the answer to the first question than the other two. Dr. Davidson also wondered whether the first episode is a distinct biological milestone on a trajectory of a dynamic process or whether it is an accumulation of environmental and social factors triggering entry into the health care system. The latter possibility is similar to that seen with dementia and other slow functional failures. There may be no clear demarcation between non-psychotic and psychotic. He emphasized that we must keep these distinctions in mind to remain clear about our findings.

Dr. Davidson has found there are environmental factors that determine the timing of the diagnosis of first episode psychosis. These include availability of informal care at home (which delays presentation), access to formal care, use of diagnostic criteria, the level of social tolerance of deviant behavior, the perceived impact of diagnosis on the patient and family, and the perceived benefit to the family. Because of these and perhaps other factors, the duration of psychosis before treatment varies widely among countries.

He stated that 3-5% of the general population of adolescents has a psychiatric diagnosis; about 7% of his study population has such a diagnosis. His population is composed of healthy draftees into the military. Their diagnoses include schizophrenia spectrum personality disorders, adjustment disorders, antisocial personality disorder, mental retardation, drug and alcohol abuse, other personality disorders, and neurosis. The risk of developing schizophrenia is highest in subjects with illnesses in the schizophrenia spectrum. The second highest risk is for subjects with adjustment disorder.

He has concluded that about 25% of schizophrenic patients have a psychiatric diagnosis before their diagnosis of schizophrenia. Roughly 75% of them do not have such a diagnosis. In contrast, he noted that 99% of adolescents with non-psychotic psychiatric diagnoses are not diagnosed with schizophrenia later.

In his final comments, Dr. Davidson reminded the audience that the dopamine receptors in the striatum are fully saturated with a 2.5 mg dose of haloperidol. Increases in dose will not lead to better efficacy. They result in more extrapyramidal side effects.