Catatonia is a severe psychomotor syndrome that includes motor, behavioral, affective and neurovegetative symptoms and signs. According to the 11th Revision of the International Classification of Diseases (ICD-11), catatonia can be diagnosed as associated to a mental disorder, as induced by substances or medication, or as secondary to medical conditions. In 80 % of cases, catatonia is thought to be associated with psychiatric disorders, such as mood disorders or schizophrenia (Oldham, 2018). In 20 % of cases, non-psychiatric conditions are found as the principal cause of catatonia, including inflammatory, autoimmune, infectious and neurodegenerative disorders, as well as traumatic or drug-related conditions (Oldham, 2018; Rogers et al., 2019; Solmi et al., 2018). In spite of the diverse etiologies of catatonia, this syndrome usually responds well to treatment. Lorazepam is used as first-line medication, and in cases of treatment-resistance, electroconvulsive therapy (ECT) is recommended (Bush et al., 1996; Solmi et al., 2018). If not recognized or rapidly treated, catatonia can lead to death via numerous complications, including infections, rhabdomyolysis, and thromboembolic phenomena (Funayama et al., 2018). The pathophysiology of catatonia is still unknown, and brain mechanisms underlying this syndrome are being studied using various neuroimaging techniques (Cattarinussi et al., 2022; Magnat et al., 2022; Walther et al., 2019). Similarly, epidemiological and clinical approaches have proven to be useful in elucidating the links between environmental factors and the development of catatonia (Mastellari et al., 2023; Rogers et al., 2021; Yeoh et al., 2022).

The analysis of seasonality has been used for the study of the different risk factors involved in psychiatric disorders (Zhang et al., 2021). Seasonality studies have largely been conducted in mood disorders and schizophrenia, allowing interesting insights into pathophysiological mechanisms and etiopathogenesis (Castrogiovanni et al., 1998; Geoffroy et al., 2014; Hinterbuchinger et al., 2020; Maruani et al., 2018; McCutcheon et al., 2020). Regarding mood disorders, for example, studies of seasonality have resulted in pathophysiological theories involving the role of circadian rhythms, core clock genes, temperature and daylight hours (Ambar Akkaoui et al., 2022; Geoffroy et al., 2015, 2014). As for schizophrenia, the role of infections during the perinatal period was suggested in the light of studies of seasonality (Watson et al., 1984). Interestingly, the role of seasonality in psychiatric disorders can also be assessed clinically, at the individual level, using psychometric instruments, such as the Seasonal Pattern Assessment Questionnaire (SPAQ) (Reynaud et al., 2021).

Although still scarce, research on seasonality of catatonia might be helpful to identify the underlying mechanisms and causes of this clinical syndrome. Moreover, for many of the disorders that can cause catatonia, a seasonal pattern has been described. In terms of psychiatric causes, studies on the seasonality of mood disorders and psychosis have been replicated several times worldwide, and have shown that seasonal patterns are associated with more severe manifestations (Bauer et al., 2021; Geoffroy et al., 2013). Considering mood disorders, depressive phases have been described as more common during early winter, while manic phases have been found to be more frequent in early summer (Geoffroy et al., 2014, 2013; Partonen and Lönnqvist, 1998). Similarly, studies of schizophrenia have shown a seasonal presentation of psychotic symptoms during the year (Hinterbuchinger et al., 2020; Owens and McGorry, 2003; Zhang and Volkow, 2023). Seasonality studies of other psychiatric disorders exist, but results have been far less replicated (Ambar Akkaoui et al., 2022; Geoffroy and Amad, 2016; Liang et al., 2018; Pires et al., 2022). Regarding non-psychiatric conditions, seasonal patterns are known for certain infections, as well as for the activity of the human immune system (Dopico et al., 2015; Fisman, 2007; Wyse et al., 2021), which both seem to play a role in some forms of non-psychiatric catatonia (Rogers et al., 2019).

Regarding the seasonality of catatonia, a seasonal pattern was recently described for the first time in a cohort of 955 patients, throughout ten years in South London (Mastellari et al., 2023). An initial peak of cases was found at the end of winter, and a second peak at the end of summer. It was suggested that this seasonal pattern of catatonia reflected the impact of the underlying psychiatric disorders, e.g., mood disorders, which show a similar seasonal pattern. However, no stratified analyses by the underlying disorder could be performed to confirm that hypothesis, due to insufficient statistical power and limited sample size. Moreover, the external validity was limited, as cases were limited to one geographic area.

The aim of the present study is to examine for a seasonal pattern in the onset of catatonia, extending previous findings in a larger independent sample and to perform subgroup analyses, stratifying by main associated psychiatric disorder (focusing on mood disorders and psychosis).