This study aims to assess the incidence, sociodemographic and clinical characteristics, treatment response, and short-term outcomes of adult patients with catatonic syndrome in the Bilbao area (Spain). Data will be collected from January 2024 to December 2025 from all patients aged 18 years or older diagnosed with catatonia of any etiology at Basurto University Hospital who provide informed consent to participate.

Catatonic syndrome is a severe neuropsychiatric condition characterized by motor, behavioral, and speech abnormalities, frequently accompanied by autonomic and affective disturbances. Although historically conceptualized as a subtype of schizophrenia, current diagnostic classifications (DSM-5, ICD 11) recognize catatonia as a transdiagnostic syndrome that may occur in association with a wide range of psychiatric, neurological, metabolic, toxic, autoimmune and other medical conditions. Early recognition is clinically relevant, as catatonia is potentially reversible and timely treatment is associated with improved short-term outcomes.

Available epidemiological data indicate marked variability in the reported incidence and prevalence of catatonia across populations and clinical settings. Population-based studies from high-income countries (UK, USA) have reported incidence rates of approximately 4-5 catatonic episodes per 100,000 person-years. In contrast, studies conducted in acute psychiatric inpatient settings have described substantially higher prevalence rates, ranging from approximately 20% to over 40% of admitted patients.

In Spain, published data are limited to selected hospital-based subpopulations. Prevalence rates of approximately 8-9% have been reported in older adults assessed by liaison psychiatry services in general hospitals, while markedly higher rates have been described in specific psychiatric inpatient samples, including geriatric psychiatry wards (nearly 40%) and patients hospitalized for first-episode psychosis (approximately 20-25%). These findings highlight the influence of age, clinical setting, and underlying diagnosis on observed prevalence estimates.

To date, however, no studies have been conducted in Spain that systematically examine the incidence or prevalence of catatonic syndrome across an unselected adult hospital population, irrespective of underlying diagnoses or specific clinical subgroups. Consequently, the epidemiology and short-term clinical course of catatonia in a general hospital setting encompassing all medical and psychiatric services remain insufficiently characterized.

This prospective observational cohort study aims to address this gap by describing the incidence, sociodemographic and clinical characteristics, comorbidity profile, treatment response, and short-term outcomes of adult patients diagnosed with catatonic syndrome at Basurto University Hospital, a general university hospital providing secondary-level care to the Bilbao area (Spain). The study includes patients attended in any hospital service, including the emergency department and inpatient medical or psychiatric units.

All consecutive patients aged 18 years or older who are diagnosed with catatonia of any etiology during hospital care between 1 January 2024 and 31 December 2025 will be eligible for inclusion. The diagnosis of catatonia will be established according to DSM-5 criteria, requiring the presence of at least three characteristic catatonic signs identified through systematic clinical assessment. In addition, the Bush-Francis Catatonia Rating Scale (BFCRS) will be administered to support diagnostic assessment and severity quantification at presentation and during follow-up. Participants will be followed prospectively throughout their hospital stay, from diagnosis until medical discharge.

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Hypotheses

Given the descriptive and observational nature of the study, the following hypotheses are formulated as expected patterns based on existing literature.

Primary hypothesis

-The incidence, sociodemographic characteristics, clinical presentation, comorbidity profile, treatment response, and short-term outcomes of catatonic syndrome observed in this study are expected to be broadly consistent with those reported in previous studies conducted in comparable healthcare settings.

Secondary hypotheses

• The incidence of catatonic syndrome in the adult hospital population is expected to fall within the range reported in population-based studies from high-income countries.
• The age distribution of catatonia is expected to show a bimodal pattern, with higher occurrence in early adulthood and later life.
• Hypokinetic presentations are expected to be more frequent than hyperkinetic or mixed forms in the hospital setting.
• Catatonic syndrome is expected to be associated with a heterogeneous range of underlying psychiatric and medical conditions, including affective and psychotic disorders as well as neurological and autoimmune conditions.
• Treatment with benzodiazepines is expected to be associated with a high rate of short-term clinical improvement.
• In the short term, catatonia is expected to be associated with an increased risk of medical complications related to immobility, without a marked increase in in-hospital mortality.

Study Variables

The following variables will be systematically collected and classified as primary and secondary variables.

Primary variable

-Annual incidence of catatonic syndrome, calculated as the number of new cases diagnosed at Basurto University Hospital per year divided by the reference population of the Bilbao catchment area, expressed as cases per 100,000 inhabitants per year.

Secondary variables

• Sociodemographic variables: age and sex.
• Catatonia-related variables: catatonia subtype (hypokinetic, hyperkinetic, or dyskinetic/mixed), BFCRS total score, and Global Clinical Impression scores at admission and discharge.
• Comorbidity variables: underlying psychiatric diagnoses and medical conditions, including neurological, autoimmune, metabolic, and toxic etiologies.
• Treatment-related variables: type of treatment administered (benzodiazepines, electroconvulsive therapy, or other pharmacological interventions) and response to benzodiazepine treatment (yes/no).
• Outcome variables: short-term clinical evolution categorized as complete recovery, incomplete recovery, lack of response, or death during hospitalization.
• Hospitalization-related variables: occurrence of medical complications during admission, length of hospital stay, and discharge destination.

Statistical Analysis

Statistical analysis will be primarily descriptive, in line with the observational design of the study. Incidence rates will be calculated annually and expressed per 100,000 inhabitants. Categorical variables will be summarized using frequencies and percentages, and quantitative variables will be described using appropriate measures of central tendency and dispersion. Missing data and losses will be documented and considered in the interpretation of results.

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Ethical and Legal Considerations

The study will be conducted in accordance with the principles of the Declaration of Helsinki and with applicable national and European legislation governing biomedical research and the protection of personal data, including Regulation (EU) 2016/679 (General Data Protection Regulation), Spanish Organic Law 3/2018 on Personal Data Protection and Guarantee of Digital Rights, and Law 14/2007 on Biomedical Research.

The study protocol has been submitted for evaluation and approval by the corresponding Research Ethics Committee. Participation is voluntary, and refusal to participate or withdrawal from the study will not affect the medical care provided.

Clinical data will be collected from electronic medical records by authorized study personnel and subsequently pseudonymized prior to analysis. Identifiable data will be stored separately from the study database under restricted access and appropriate technical and organizational security measures.

Written informed consent will be obtained from participants or their legal representatives whenever clinically feasible. In cases of acute catatonia in which the patient lacks decision-making capacity at the time of diagnosis, informed consent will be sought once clinical recovery allows adequate understanding (deferred consent). In the event of in-hospital death before consent can be obtained, clinical data may be included in accordance with ethical committee guidance and applicable legal provisions, in order to minimize information bias.

The study does not involve any additional diagnostic procedures or therapeutic interventions beyond standard clinical care. No financial compensation is provided to participants, and no commercial funding is involved. Study results will be disseminated through scientific publications and presentations, ensuring full confidentiality of participant data.

Inclusion Criteria

• Age ≥ 18 years at the time of hospital care.
• Diagnosis of catatonic syndrome established according to DSM-5 criteria.
• Patients attended at Basurto University Hospital in any clinical setting, including the Emergency Department or inpatient physical or psychiatric units.
• Diagnosis made during the study period, from 1 January 2024 to 31 December 2025.
• Catatonia of any etiology, including psychiatric, neurological, medical, metabolic, toxic, or autoimmune causes.
• Provision of informed consent by the patient or their legal representative, when clinically feasible; deferred consent accepted in cases of acute catatonia.

Exclusion Criteria

• Refusal to participate in the study by the patient or their legal representative.
• Withdrawal of informed consent at any point during the study.

The study population consists of adult patients aged 18 years or older who are attended at Basurto University Hospital, a general university hospital providing secondary-level care to the Bilbao area (Spain), and who are diagnosed with catatonic syndrome during routine hospital care. Eligible participants include patients evaluated in any clinical setting, including the Emergency Department and inpatient medical or psychiatric units. Catatonia is diagnosed according to DSM-5 criteria and supported by systematic clinical assessment and severity quantification using the Bush-Francis Catatonia Rating Scale. Patients with catatonia of any etiology are included, reflecting an unselected adult hospital population.