Elsevier

Schizophrenia Research

Volume 44, Issue 2, 3 August 2000, Pages 113-120
Schizophrenia Research

Schizophrenia and birth order in Pakistan

https://doi.org/10.1016/S0920-9964(99)00221-2Get rights and content

Abstract

The paper describes a two stage study. In Stage I the birth orders of 453 adult patients with different diagnoses, seen in the routine work of a general hospital psychiatry department, were compared. Patients with schizophrenia had significantly higher average birth positions than patients with other diagnoses, even after controlling for sibship size.

In Stage II, the birth positions of 64 patients with schizophrenia (DSMIIIR) were subjected to a goodness-of-fit chi-square test. Over-representation of eldest siblings was highly significant for both sexes. When patients aged 30 and above were analysed separately, there was still a significant excess of first-born.

These findings are in contrast to birth order studies of schizophrenia in western populations. In the authors' opinion, they can not be accounted for by the biases to which birth order studies are prone. They indicate a need for further community-based studies.

Introduction

The relationship between birth order and schizophrenia is a relatively unexplored field, with few recent studies in either developed or developing countries.

Traditional Pakistani society is highly suitable for birth order research. The first and most obvious factor is the large size of families compared with industrialised countries. Secondly, birth order studies in many industrialised societies have been made virtually impossible by high rates of marital breakdown and remarriage, resulting in blended families. In Pakistan, blended families result from divorce and remarriage (as in ‘western’ societies) and also from polygamous marriages. However, although such marriages tend to confound the interpretation of birth order data, they represent only a small proportion of the total number of marriages in Pakistan. Thirdly, virtually everybody in traditional Pakistani society marries. Remaining single is not regarded as an option and parents have a social and moral duty to find mates for their children. This produces a uniformity in the society which facilitates study.

Barry (1967) reported that the first-born in Asia have been found, with some possible exceptions, to be more susceptible to schizophrenia. He showed an over-representation of first-born siblings in upper class American families and wrote that this finding was “opposite in direction to most reported samples of American schizophrenics.”

Schooler (1961) combined his own figures with those of other published studies and found that a significantly higher proportion of patients with schizophrenia were last-born than were first-born. Farina et al. (1963) reported on a series of hospitalised schizophrenia sufferers. They found that significantly more had been born in the last than in the first half of the birth order in large sibships (five or more children).

The association between schizophrenia and obstetric complications has been reviewed by McNeil (1995). In a Swiss series Gunther-Genta et al. (1994) found birth order to be related to eight obstetric items but only prolonged delivery was more frequent in patients with schizophrenia, being more common in first and only siblings. However, the difference was not statistically significant. Umbilical cord problems and atypical foetal presentation were also more frequent in patients with schizophrenia, but neither of these two complications was related to birth order. However, Jacobsen and Kinney (1980) did find a significant increase in the frequency of prolonged labour in patients with schizophrenia as compared to controls.

The viral hypothesis for schizophrenia has been studied with respect to birth order. Sham et al. (1993), using data from a Swedish family study, found that the risk of schizophrenia was less in first-born siblings and higher in individuals who had had siblings three to four years older while they were in utero. The authors regarded this as indirect support for the maternal viral infection hypothesis, since respiratory viral infections are frequently brought into the home by young children.

Difficulties associated with interpreting birth order data have resulted in a relative dearth of research activity in recent years. This may be partly due to the difficulty in avoiding bias in the study sample. Price and Hare (1969) described the sources of bias to which birth order studies are prone. Firstly, changes in the number of births from year to year; secondly, movement in or out of the population; thirdly, incompleteness of sibships; and fourthly exclusion of siblings or sibships from analysis.

In the present study, the intention of the first statistical analysis was not to study schizophrenia. However, the marked difference between schizophrenia and other diagnostic groups changed the focus of attention to schizophrenia. The aim of Stage II of the study was to examine the birth order of patients with schizophrenia in Pakistan with a larger, more rigorously selected population, and to confirm the finding of Stage I that patients with schizophrenia came from elder children in sibling groups.

Section snippets

Methods

The Memorial Christian Hospital in Sialkot, Pakistan is a 300 bed general hospital. Sialkot, has a population of approximately 300 000 and is the main city of Sialkot District which has a population of about 2 million. The principal author was one of three psychiatrists working in the district.

Results

Sibship sizes in both stages are shown in Table 1.

Discussion

The study shows that, in the Pakistani patients studied, patients with schizophrenia had a significantly higher mean rank birth order than patients with other diagnoses. Eldest siblings were over-represented in the schizophrenia group, even after correcting for sibship size. When patients with schizophrenia were studied alone, the observed number of eldest siblings was highly significantly greater than the calculated expected value.

The limitations of Stage I were as follows. Firstly, clinical

Acknowledgments

We would like to thank Prof. M. Rashid Chaudhry, Dr. Habibullah Chaudhary and Dr. Shamshad A. Gill for granting access to their patients; also Prof. A.C.P. Sims and Mss. Amanda Farrin and Vicki Allgar, statisticians, for advice on statistics and preparation of the manuscript.

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