Summer Birth and Deficit Schizophrenia in the Epidemiological Catchment Area Study ERICK MESSIAS, M.D., and BRIAN KIRKPATRICK, M.D. 1 Winter birth is a widely replicated risk factor for schizophrenia. However, previ- ous studies have suggested that patients with the deficit syndrome of schizophrenia have an excess of summer births. We tested the summer birth effect in a population- based study. Data came from the Epidemiological Catchment Area study, which had a representative sample of the U.S. population. Psychotic patients with features of the deficit syndrome had a significant association with summer birth, compared with the general population. There was also a significant association between summer birth and the deficit syndrome within the psychotic population, after accounting for the variance due to disorganization, hallucinations and delusions, and demographic characteristics. These findings add to the evidence suggesting the etiopathophysiology of the deficit group differs from that found in other patients with schizophrenia. —J Nerv Ment Dis 189:608 –612, 2001 Risk factors are often important clues to the eti- ology of a disease. Some of the risk factors for schizophrenia relate to very early events in the pa- tient’s gestation and delivery, such as maternal in- fections during pregnancy (McGrath and Castle, 1995), the mother’s exposure to other significant stresses (Machon et al., 1997; Myhrman et al., 1996; van Os and Selten, 1998), or a complicated labor (Dalman et al., 1999). These findings have changed thinking about the etiology of schizophrenia and have influenced subsequent studies in other areas of schizophrenia by focusing on very early brain devel- opment. Winter birth is a widely replicated risk factor for schizophrenia (Torrey et al., 1997). A 1986 review of this evidence suggested patients born in the winter had a relatively benign form of schizophrenia (Boyd et al., 1986). Some other studies have also found that winter-born patients had distinguishing clinical (Hsieh et al., 1987; Nasrallah and McCalley-Whitters, 1984), anatomical (Degreef et al., 1988; Sacchetti et al., 1992; Zipursky and Schulz, 1987), or demo- graphic features (Franzek and Beckmann, 1996; Ohlund et al., 1991) We previously reported that patients with the def- icit syndrome of schizophrenia had an excess of summer births (Kirkpatrick et al., 1998, 2000). This finding is of theoretical interest, as confirmation of a distinctive risk factor would suggest there are im- portant differences in etiology in deficit and non- deficit groups. A different risk factor would not be surprising, in light of other studies showing biolog- ical and clinical differences between deficit and non- deficit groups, including studies of structural (Buchanan et al., 1993) and functional imaging (Tamminga et al., 1992), cognitive processing (Buchanan et al., 1990), course variables, and treat- ment response (Fenton and McGlashan, 1992, 1994; Kopelowicz et al., 1997) as well as histologic brain differences (Kirkpatrick et al., 1999). Patients with the deficit syndrome have primary (or idiopathic) negative symptoms that are enduring features (Carpenter et al., 1988). The correlates of negative symptoms as defined by the widely used rating scales also differ from those of the deficit syndrome (Kirkpatrick et al., 1993, 1996a, 1996b, 1996c) We tested the hypothesis that the deficit syn- drome was associated with summer birth by using a population-based study from the United States. The dataset we used permitted a comparison to a non- psychotic population that had been assessed at the same time as the psychotic group, and using the same methods. Methods The Epidemiological Catchment Area study (ECA) was conducted in the 1980s in five sites 1 Maryland Psychiatric Research Center, Department of Psy- chiatry, University of Maryland, Baltimore, Maryland. Send re- print requests to Dr. Kirkpatrick, Maryland Psychiatric Research Center, P.O. Box 21247, Baltimore, Maryland 21228. This work was supported in part by PHS grant MH 40279 and R29 grant MH 60487. 0022-3018/01/1899 –608 Vol. 189, No. 9 THE JOURNAL OF NERVOUS AND MENTAL DISEASE Printed in U.S.A. Copyright © 2001 by Lippincott Williams & Wilkins 608