Seasonal influences on admissions for affective disorder and schizophrenia in Ireland: a comparison of first and readmissions

Abstract

Although genetic and environmental factors operating before or around the time of birth have been demonstrated to be relevant to the aetiology of the major psychoses, a seasonal variation in the rates of admission of such patients has long been recognised. Few studies have compared first and readmissions. This study examined for seasonal variation of admission in the major psychoses, and compared diagnostic categories by admission status. Patients admitted to Irish psychiatric inpatient facilities between 1989 and 1994 with an ICD-9/10 diagnosis of schizophrenia or affective disorder were identified from the National Psychiatric Inpatient Reporting System (NPIRS). The data were analysed using a hierarchical log linear model, the chi-square test, a Kolmogorov-Smirnov (KS) type statistic, and the method of Walter and Elwood. The hierarchical log linear model demonstrated significant interactions between the month of admission and admission order (change in scaled deviance 28.77, df = 11, P < 0.003). Both first admissions with mania, and readmissions with bipolar affective disorder exhibited significant seasonality. In contrast, only first admissions with schizophrenia showed significant seasonal effects. Although first admissions with mania and readmissions with bipolar disorder both show seasonality, seasonal influences appear to be more relevant to onset of schizophrenia than subsequent relapse.

Involuntary admissions in Italy: the impact of seasonality

“…Studies concerning hospitalizations of schizophrenic patients are conflicting. A seasonal variation has been reported with a summer peak in all admissions (Clarke et al 1999;Shiloh et al 2005) or in the first admission (Takei et al 1992); other studies show a correlation between hospitalizations and early spring (Tian et al 2006) or winter (Davies et al 2000). Lastly, no seasonal pattern has been found by several authors (Modai et al 1994;Amr & Volpe 2012).…”

Seasonal influences on first-episode admission in affective and non-affective psychosis

“…One of the few studies analyzing this indicated that in BPAD, first admission and readmission show a seasonal pattern. However, in schizophrenia, only first admissions show a seasonal peak (41). Alternatively, other studies found seasonality in chronic, not in FE, patients with schizophrenia (42).…”

Evidence for Seasonal Mania

“…[1][2][3][4][5] However, the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) includes the specifier "with seasonal pattern" only for depression. 6 Thus, patients cannot be classified as having "seasonal" affective disorder if their manic episodes occur in a particular season but they do not have seasonal depression.…”