Longer duration of breastfeeding associated with reduced risk of developing schizophrenia

Schizophrenia has a lifetime prevalence of approximately 1%, although this may vary between locations. It is a serious disease with far-reaching consequences, often with devastating effects on the lives of patients and their families. It is also a major contributor to health care expenditure, to such an extent that the cost of caring for these patients accounts for 2.5% of all health care expenditure in the USA.


Objectives
The study aimed to determine whether there were any differences in the breastfeeding practices of mothers of patients with schizophrenia compared with non-psychiatric age-and gendermatched controls.

Methods
The study was approved by the Ethics Committee of Stellenbosch University.All subjects signed written, informed consent.Fifty Background.Some studies have suggested that breastfeeding may be protective against the development of schizophrenia.
Such a theory supports the neurodevelopmental hypothesis of schizophrenia.
Objective.To determine whether there were differences in breastfeeding patterns between patients with schizophrenia and controls.
Method.Fifty subjects with schizophrenia and 50 age-and gender-matched controls were included in the study.All subjects and their mothers were interviewed using a structured questionnaire to determine the extent of breastfeeding in infancy and age of onset of psychosis.
Results.There was a significant difference in the duration of breastfeeding in patients versus controls (p < 0.05).

Study design
The investigator (MSH) contacted the mothers of the 50 subjects.
Personal interviews were conducted either telephonically or face to face.After obtaining informed consent from both the subjects and their mothers, the following information was sought: (i) age and gender of the patient; (ii) whether the patient was breastfed as an infant -breastfeeding was defined as having been put to the breast at least once; (iii) if the subject was breastfed, the duration of breastfeeding; and (iv) age of onset of schizophrenia.
Controls were recruited from within Tygerberg Hospital.After verbal and written consent had been given, the mothers of controls were asked: (i) the age and gender of controls; (ii) whether the control patient was breastfed as an infant; (iii) if breastfed, the duration of breastfeeding; (iv) whether the control patient suffered from any psychiatric disease; and (v) whether the control patient suffered from any other disease that might affect outcome.
Results are expressed as means ± standard deviation (SD).
Student's t-tests were used to compare the groups, and a significance level of 0.05 was used throughout.

Results
The investigator was able to contact and interview the mothers of all the subjects and controls.The patient group comprised 12 females and 38 males aged 21.7 ± 8.6 years, and the control group 11 females and 39 males aged 21.7 ± 8.6 years.
The duration of breastfeeding for the patient group was 8.6 ± 11.31 months and for the control group 14.24 ± 16.58 months.
There was not a significant correlation between the duration of breastfeeding and the age of onset of psychosis.

Discussion
Our findings seem to support the hypothesis that breastfeeding may offer some protection against the later development of schizophrenia.Although we did not find a statistically significant difference in the number of patients who were breastfed compared with controls, there was a trend toward such a difference.In 2003 Amore and colleagues 12 did a study comparing the breastfeeding history of 113 patients with 140 of their siblings and 113 healthy controls.There were no significant differences between the groups, although a positive correlation was found between duration of breastfeeding and age of onset of illness.
Although the potential mechanisms by which breastmilk may play a protective role are numerous, our findings are compatible with the membrane phospholipid hypothesis of schizophrenia.The latter hypothesis suggests that disturbed phospholipid metabolism is the fundamental cause of schizophrenia.It is postulated that in individuals who develop schizophrenia there is an accelerated rate of loss of unsaturated fatty acids, notably arachidonic acid (AA), docosahexanoic acid (DHA) and eicosapentanoic acid (EPA). 2 When present to a mild degree, the increased rate of loss will be compensated for by an increased incorporation of phospholipids into the membrane, with no loss of phospholipid composition, but when present to a greater degree, or in association with problems in incorporation, there will be an actual change in membrane composition 2 which may then manifest later as the syndrome of schizophrenia.
The human brain undergoes a growth spurt during the last trimester of pregnancy and the first few months postnatally. 13This requires an abundant supply of essential fatty acids (EFAs).While in utero, the baby gets its supply of EFAs from the mother, but after birth adequate amounts must be supplied in feeds.Human milk contains small but significant amounts of polyunsaturated fatty acids (PUFAs).PUFAs are present in the milk of lactating women throughout lactation.The total percentage of saturated fatty acids progressively increases with time, while the total amount of monounsaturated fatty acids in breastmilk decreases during the first 12 months of lactation.The concentrations of DHA and AA remain stable throughout the nursing period. 14 is well established that pre-term and full-term infants fed on formula feeds have lower plasma and erythrocyte levels of DHA and AA than breastfed infants. 15,16Several studies [17][18][19] have shown a correlation between infant feeding and the development of neuropsychiatric disorders.There is further, growing evidence that functional neurodevelopment is abnormal in infants and children who later develop schizophrenia.PUFAs, particularly AA and DHA, are essential to brain development, and a relative lack of these PUFAs has been associated with cognitive and neurological deficits similar to those seen in bottlefed preterm infants. 20Any such predisposition is likely to be exacerbated by a poor dietary supply of PUFAs. 20her mechanisms by which breastfeeding and schizophrenia may interact should clearly also be considered.These would include: (i) the psychological effects of breastfeeding on both mother and infant with effects on bonding and nurturing; 21 (ii) the possibility that minor neurological abnormalities, so common in patients with schizophrenia, may make it difficult or even impossible for the mother to breastfeed; subjects were recruited from the inpatient wards at Stikland and Tygerberg hospitals in Cape Town.All subjects met Diagnostic and Statistical Manual for Mental Disorders (DSM-IV) criteria for a diagnosis of schizophrenia.The following patients were excluded: (i) those with unclear diagnosis, specifically with co-morbid substance abuse; (ii) patients with neurological disorders; (iii) patients known to be Longer duration of breastfeeding associated with reduced risk of developing schizophrenia M S Hartog, MB ChB, MMed (Psych) P P Oosthuizen, MB ChB, MMed (Psych), FCPsych (SA), Phd R A Emsley, MB ChB, MMed (Psych), FCPsych (SA), MD Department of Psychiatry, Stellenbosch University, W Cape 8 and (iii) shared risk factors such as poor mothering skills or adverse home environment which may lead to reduction in the chance of the infant being breastfed as well as having psychological consequences that may be risk factors for schizophrenia.20 ConclusionOur study reports modest evidence for an association between breastfeeding and schizophrenia.Compared with controls,Volume 13 No. 2 June 2007 -SAJP articles