Several observations have suggested that neurodevelopmental problems associated
with
schizophrenia represent antecedents rather than consequences of the
disorder. The concept of an unknown brain legion is a hypothetical construct
that has been supported by evidence such as the latitude effect, which
indicates that individuals who live at higher
latitudes show an increased risk
for developing more malignant forms of
schizophrenia. The prenatal environment
and gestation period may also play an important role. The seasonality
effect describes findings that births occurring in late winter or early spring
are associated with a higher risk for developing schizophrenia, especially when
temperatures were very low the previous fall. Both the latitude effect and the
seasonality effect, however, may point to the mother having contacted some viral
infection, or developed some autoimmune response.
Support for this theory can also be drawn from the evidence that the influenza
epidemic of 1957 was associated with an increased rate of schizophrenia. Also,
in times of severe food shortage, such as during the
Hungerwinter of 1945 in
the Netherlands, children show an increased risk of developing schizophrenia
(though this was true only for female offspring whose mothers were in their
first trimester during the Hungerwinter). Further proof of the importance of
the gestation period is seen by the fact that monozygotic twins who are
discordant for schizophrenia are also discordant for fingerprint ridge count,
which is formed in the second trimester.
Certain qualities are associated with a better course and outcome. Individuals
who had a good pre-morbid adjustment or who were doing well before the onset of
the disorder tend to have a higher chance of recovery. Other qualities
associated with a better outcome include: later age of
onset, acute rather than a gradual, insidious onset, brief duration of active
phase
symptoms, good inter-episode functioning, minimal residual symptoms, no
structural brain abnormalities, and no family history of schizophrenia or mood
disorders.
