prodrome

Meaning: A prodrome (prodromal phase) is the stretch of time before a disorder's defining symptoms emerge, when milder or less specific changes show up. In schizophrenia the typical course has three phases: prodromal, active, and residual. Prodromal signs include social withdrawal, falling grades or work performance, poor self-care, flattened emotion, and unusual ideas or perceptions that fall short of full delusions or hallucinations. The active phase brings positive symptoms (hallucinations, delusions, disorganized speech or behavior), often with negative symptoms. In the residual phase the florid symptoms lessen, though some negative symptoms or odd beliefs can linger.

On the MCAT: A vignette describes a teenager or young adult who gradually withdraws from friends, does worse at school, and voices strange ideas. Months later hallucinations begin. You may be asked which phase the early period represents, or to put the phases in order. Passages may also discuss early detection or intervention.

Common confusion: Prodromal and residual phases can look alike, since both involve milder symptoms without full psychosis. The difference is timing. A prodrome comes before the first active phase, and the residual phase comes after it. A prodrome is also not a diagnosis. It is usually identified in hindsight, and some people with similar early signs do not go on to develop the disorder.