Season of birth and schizophrenia: A response to the Lewis and Griffin critique.

Abstract

A number of writers have published data suggesting that schizophrenics are particularly likely to have been born in the winter months. Lewis and Griffin have argued that this "seasonally" effect may be an artifact resulting from (a) the use of inappropriate expected values in the calculation of chi-squares in previous studies; (b) the age-incidence effect-the tendency of risk to increase with time in disorders whose incidence increases with age; and (c) the ageprevalence effect-the fact that people born early in a reporting period have been at risk for any disease longer than those born later in that period. We studied the birth months of 3,556 schizophrenics at a Minnesota Veterans Administration hospital before and after instituting corrections for year-to-year across-month variations in birthrates in our expected values and the age-prevalence bias toward the January-March seasonality effect described in some earlier studies. Finally, we reanalyzed our data on a subset of patients in whom the age-incidence effect should be minimal. Even after these corrections the results supported the contention that the winter birthrate for schizophrenics is excessive, at least in severe climates.More than a dozen papers have appeared describing seasonality effects in schizophrenia-reported tendencies for an excessive number of schizophrenic births to occur in the winter months. This research is particularly important because it suggests that season-related factors-winter cold, summer heat, infectious diseases, prenatal nutritional deficiencies, and so forth-may play a role in the development of schizophrenia.Recently, Lewis and Griffin (1981) have argued that the seasonality effect may be an artifact resulting from three weaknesses in the designs of studies in which it has been reported. First, they point out (as had Hare, 1975) that the expected values used in the chi-squares employed to determine whether the frequency of schizophrenic births in the winter months is proportionately higher than that for the general population are typically based on a pool of many years and do not

Abandoning the concept of ‘schizophrenia‘: Some implications of validity arguments for psychological research into psychotic phenomena

“…For example, Sarbin & Mancuso (1980) surveyed the Journal of Abnormal and Social Pychology (later the Journal of Abnormal Pychology) for the years 1959 1978 and found that 374 papers, filling a total of 2472 pages o r 15.3 per cent of the journal space, employed the presence o r absence of schizophrenia as an independent variable. Hypotheses that have been proposed to account for schizophrenic breakdowns have implicated nearly every variable known t o affect human behaviour, including brain biochemistry (Green & Costain, 1981), genetic endowment (Gottesman & Shields, 1982), neurological factors (Pincus & Tucker, 1978), diet (Singh & Kay, 1976); season of birth (Watson, Kacula, Anguluski & Bruun, 1982), hypothesized viral agents (Crow, 1984), social stress (Faris & Dunham, 1939), life-events (Brown & Birley, 1968) and family structure (Bateson, Jackson, Haley & Weakland, 1956).…”

The birth seasonality effect in nonschizophrenic psychiatric patients

“…We (Watson, Kucala, Angulski, & Brunn, 1982) attempted to control the ageprevalence effect (and, to some degree, the age incidence effect) in a paper on schizophrenic birth seasonality by studying the birth months of schizophrenics using both January-December and July-June calendar years. We found highly significant winter birth excesses in these patients both before and after instituting that control.…”

Differences between schizophrenics born in winter and summer

“…Many studies, especially in countries of the northern hemisphere, have reported that more schizophrenics are born during winter and early spring than during other seasons (1)(2)(3)(4)(5)(6)(7)(8). These investigations suggests that some environmental influence acting in utero or in the early months of life, and varying with the season of year, contributes to the etiology of at least some forms of schizophrenia (such as viral infection, obstetric or perinatal complications, malnutrition, vitamin deficiency or temperature) (9,10).…”