November 2001

Asphyxia at birth appears to increase an individual's risk of developing schizophrenia in adulthood, a population-based study shows.

Christina Dalman (Community Medicine Unit for Psychosis Research, Stockholm, Sweden) and colleagues report that their study confirms other research for the association between fetal or neonatal damage to the central nervous system and schizophrenia. But unlike many other studies, they have taken into account confounding factors.

Using the Stockholm County In-Patient Register and community register, Dalman's team identified 524 cases of schizophrenia and 1,043 controls, matched for age, gender, hospital, and parish of birth. Birth records were used to obtain data on obstetric complications.

Signs of asphyxia at birth (Apgar score <7), the need for the child to remain in hospital, low birth weight (<2,500 g), and delay in gaining weight after birth, were all associated with significantly increased risk of schizophrenia. Pre-eclampsia, being small for gestational age, and short gestation (<33 weeks) also showed increased risk estimates, but were not statistically significant.

However, after adjusting for possible confounding factors, such as other obstetric complications, maternal history of psychotic illness, and social class, it was only signs of asphyxia at birth that remained significantly associated with an increased risk of schizophrenia.

Dalman et al report that, because different obstetric complications are often interrelated, the causal pathways for this increased schizophrenia risk are difficult to discern.

Nevertheless, they suggest that disorders such as pre-eclampsia could reduce the supply of nutrients, including glucose and oxygen, which would interfere with brain development.

'In contrast, an infant who has developed normally may experience relatively short-term insult around the time of birth because of hypoxia,' the team comments.

Hypoxic brain damage is particularly seen in the brain-stem nuclei, hippocampus, and cortex, and Dalman's team point out that recent studies have shown a reduced volume of the hippocampus in schizophrenic patients with a history of obstetric complications.

Reporting in the British Journal of Psychiatry, the authors say that minimizing the occurrence of asphyxia and subsequent states of hypoxia and ischemia could be important in preventing psychiatric conditions.

Br J Psychiatry 2001; 179: 403–408