**4. The prodrome**

Although there is great variability between patients in how their prodromes manifest, certain symptoms and signs have been frequently described. These include depressed mood, anxiety, irritability and aggressive behavior, suicidal ideation and attempts, and substance use. The most commonly occurring prodromal symptoms, according to retrospective studies of patients with schizophrenia and schizophreniform disorder, are reduced concentration and attention, reduced drive and motivation, depression, sleep disturbance, social withdrawal, suspiciousness, deterioration in role functioning, and irritability [1].

Studying these symptoms, we observe two things. First, many of them are nonspecific occurring frequently in the prodromes of nonpsychotic threshold syndromes. Second, a considerable amount of psychiatric symptoms, disability, self-harming, and other health-damaging behaviors, occur during this prodromal phase, even in the earliest stages [1, 19, 22, 39].

Cognitive, affective, and social disturbances known as "basic symptoms" are also commonly described in the early prodromal phases. This concept of "basic symptoms," developed in the 1960s, has significantly influenced the new area of prodromal research [1].

5–10% of the general population experience attenuated or subthreshold form of psychotic symptoms like transient perceptual symptoms; suspiciousness; reference and bizarre delusional ideas (e.g., the beliefs that others may be thinking badly about or laughing at); nonattendance at school, university, or work; and altered behavior toward family and friends [1, 16].

The difference between these phenomena and clear psychotic symptoms is due to their intensity, frequency, duration, and deleterious effects on the individual functionality of the person.

Neurocognitive deficits in particular impaired attention, spatial and verbal memory, and speeded information processing are also evident in the prodromal phase but at a lower degree of severity comparing to those found in first-degree relatives of patients with schizophrenia or in fully affected patients [1].

Specific cognitive deficits may be related more directly to affected brain structures and candidate genes and so may be more directly predictive of psychosis.
