Oxygen Deprivation at Birth Linked to Schizophrenia

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NEW YORK (Reuters Health) - Many studies have reported that adults
with schizophrenia seem to have had more birth complications than
non-schizophrenics. A recent study homes in on the specific
birth-related factors associated with the development of this
disorder.

In particular, obstetrical complications that deprive the baby of
oxygen--a condiiton known as hypoxia--appear to be linked to an early
onset of schizophrenia, according to a team of researchers led by Dr.
Tyrone D. Cannon of the University of California, Los Angeles.

Cannon and colleagues analyzed prenatal and birth records for 80
randomly selected patients with schizophrenia born in Finland in
1955, along with records of 61 siblings without the disease and 56
nonrelated adults matched for age, gender, and social class. The
investigators looked at a variety of prenatal and birth-related
complications.

The schizophrenic patients were divided into two groups according to
when psychotic symptoms first appeared. Early onset was defined as
symptoms appearing before age 22 for women and before age 19 for men.

The researchers found that prenatal infection, fetal growth
retardation and social class were not related to the development of
schizophrenia, but obstetrical complications around the time of birth
that deprived the baby of oxygen did appear to play a role. These
kinds of complications doubled the likelihood of developing
early-onset schizophrenia, but were not related to later onset of the
disease.

In fact, for each complication that contributed to hypoxia, the risk
of early-onset schizophrenia increased, so that patients who had been
exposed to three or more complications were 10 times more likely to
develop the disease than those with no complications.

Writing in the May issue of the American Journal of Psychiatry, the
authors note that the complication most strongly related to early
development of schizophrenia was birth asphyxia, in which the baby is
temporarily deprived of oxygen.

``The principal finding of this study is that hypoxia-associated
obstetric complications, but not prenatal exposure to infection or
fetal growth retardation, are associated with a higher than normal
risk for early-onset schizophrenia,'' the researchers conclude.

Cannon and colleagues point out that the siblings of schizophrenics
did not have any more exposure to obstetric hypoxia than normal,
which suggests that the birth complications were not caused by the
same genetic factors that lead to the disease.

The authors also note that hypoxia by itself did not predict
schizophrenia, since most subjects who had had the complication did
not become schizophrenic. And since one third of the schizophrenic
patients were not exposed to hypoxia at birth, this complication is
not the only factor in the development of the disease, the research
team explains.

Cannon's group suggests that among individuals who are genetically
predisposed to develop schizophrenia, lack of sufficient oxygen at
birth may result in a reduction of nerve connections in the parts of
the brain that produce psychotic symptoms. This idea is supported by
the fact that the same area of the brain that is most affected by
obstetric hypoxia (the temporal lobe) is also linked to schizophrenia.

SOURCE: American Journal of Psychiatry 2000;157:801-807..