Schizophrenia 195Box 24.1 provides examples of some of the symptoms that can occur
during a psychotic episode. Schizophrenic symptoms are fairly similar at
all ages, though passivity phenomena and poverty of thought are less
prominent than in adult-onset schizophrenia. In line with developmental
level, delusions in children are generally less complex than in adults, and
less likely to have sexual or other adult themes.
Schizophrenia characteristically involves a mixture of psychotic episodes
(with prominent positive symptoms) and a progressive accumulation of
negative symptoms. In the long term, it is generally the negative symptoms
that are more disabling, and more upsetting to relatives. Though DSM-IV
and ICD-10 have fairly similar diagnostic criteria for schizophrenia, DSM-
IV puts greater weight on the accumulation of negative symptoms, while
ICD-10 puts more weight on the episodic psychotic symptoms. On the
one hand, this makes the DSM-IV criteria harder to apply in the short
term since it takes a while to be sure about the accumulation of negative
symptoms. On the other hand, the DSM-IV criteria are more specific in the
long term when it comes to distinguishing schizophrenia from affective or
drug-induced psychoses. Mania in adolescence can easily be misdiagnosed
as schizophrenia in the short term – until it becomes clear that the acute
psychotic episodes are linked to mood variation and are not accompanied
by accumulating negative symptoms.
Antecedents of schizophrenia
Schizophrenia beginning in childhood or adolescence is particularly likely
to be preceded by premorbid abnormalities in development and social
adjustment. Neurodevelopmental abnormalities include speech and lan-
guage delay, clumsiness, inattentiveness, and lowered IQ (mean around
85). The onset of frank psychosis is often preceded by years of poor
social adjustment, and sometimes by disturbances of perception and
thinking that are milder variants of schizophrenic delusions and hallucina-
tions; sometimes it is preceded by disruptive behaviour disorders. Though
this premorbid picture is often clear in retrospect, it is not sufficiently
characteristic to permit a confident prospective diagnosis of incipient
schizophrenia.
Differential diagnosis
Affective psychoses and drug-induced psychoses are the most likely al-
ternative explanations for a psychotic disorder. In affective psychoses,
the psychotic episodes occur during periods of abnormal mood, and full
recovery between episodes is more likely and more complete than in
schizophrenia – hence the importance of a careful history and mental
state examination in making the distinction. It is, however, important to