Cross‐sectional and within‐subject seasonality and regularity of hospitalizations: A population study in mood disorders and schizophrenia

Abstract

Background Seasonal peaks in hospitalizations for mood disorders and schizophrenia are well recognized and often replicated. The within‐subject tendency to experience illness episodes in the same season, that is, seasonal course, is much less established, as certain individuals may temporarily meet criteria for seasonal course purely by chance. Aims In this population, prospective cohort study, we investigated whether between and within‐subject seasonal patterns of hospitalizations occurred more frequently than would be expected by chance. Methods Using a compulsory, standardized national register of hospitalizations, we analyzed all admissions for mood disorders and schizophrenia in the Czech Republic between 1994 and 2013. We used bootstrap tests to compare the observed numbers of (a) participants with seasonal/regular course and (b) hospitalizations in individual months against empirical distributions obtained by simulations. Results Among 87 184 participants, we found uneven distribution of hospitalizations, with hospitalization peaks for depression in April and November (X2(11) = 363.66, P < .001), for mania in August (X2(11) = 50.36, P < .001) and for schizophrenia in June (X2(11) = 70.34, P < .001). Significantly more participants than would be expected by chance, had two subsequent rehospitalizations in the same 90 days in different years (7.36%, bootstrap P < .01) or after a regular, but non‐seasonal interval (6.07%, bootstrap P < .001). The proportion of participants with two consecutive hospitalizations in the same season was below chance level (7.06%). Conclusions Psychiatric hospitalizations were unevenly distributed throughout the year (cross‐sectional seasonality), with evidence for regularity, but not seasonality of hospitalizations within subjects. Our data do not support the validity of seasonal pattern specifier. Season may be a general risk factor, which increases the risk of hospitalizations across psychiatric participants.

Examination of the impact of COVID-19 public health quarantine measures on acute mental health care services: A retrospective observational study

“…However, the number of admissions to acute care psychiatry at the QEII Health Sciences Centre was stable across months in 2019, with quarterly numbers ranging from 121-162, suggesting minimal seasonal differences. Additionally, research into seasonality in psychiatric admissions has not been consistent with a seasonal pattern that is specific to psychiatric diagnoses ( Bakstein et al, 2020 ).…”

Changing trends in psychiatric emergency service admissions during the COVID-19 outbreak: Report from a worldwide epicentre

“…The time period selected as comparison (from December 2019 to February 2020) might have in some way biased our results: 1) it usually includes Christmas Holidays which might affect medical assistance due to staff reduction 2) it is in a different season, and some psychiatric disorders, such as bipolar disorder, show a seasonal pattern with a tendency to relapses in specific seasons ( Geoffroy et al, 2014 ). Nevertheless, a seasonal pattern has not been clearly identified in other psychiatric disorders, and recent studies showed contrasting results ( Bakstein et al, 2019 ; Jahan et al, 2020 ). Also, we do not report significant changes in numbers of monthly admissions from January 2019 to February 2020, as reported in Figure 1 A.…”

Clinical correlates of seasonality in bipolar disorder: A specifier that needs specification?

“…“Seasonality” is a term used to describe a driving force that has a major effect on the spatiotemporal dynamics of natural systems and their populations 1 . Seasonal variations may impact the prevalence, course, and expression of several medical diseases, 2,3 as well as symptom intensity and/or presentation in severe mental disorders 4‐6 …”

“…Bipolar disorder (BD) presents recurrent acute episodes characterized by changes in energy levels and behavior with emotional and thought dysfunction 7,8 . Some patients with BD present a tendency toward relapses according to specific moments of the year, with reported rates ranging from 15% to 25% 6,9 . Classical descriptions of seasonal variations are observed worldwide and depict possible manic/hypomanic peaks, major in spring‐summer and milder in autumn, depressive peaks major in early winter, and milder in spring‐summer, and mixed episodes peak in early spring or mid/late summer 10 …”

“…1 Seasonal variations may impact the prevalence, course, and expression of several medical diseases, 2,3 as well as symptom intensity and/or presentation in severe mental disorders. [4][5][6] Bipolar disorder (BD) presents recurrent acute episodes characterized by changes in energy levels and behavior with emotional and thought dysfunction. 7,8 Some patients with BD present a tendency toward relapses according to specific moments of the year, with reported rates ranging from 15% to 25%.…”