¹Mental Health Institute - Hospital del Mar (Parc de Salut Mar), Addiction Programme, Barcelona, Spain, ²Mental Health Institute - Hospital del Mar (Parc de Salut Mar), Day Hospital Programme, Barcelona, Spain, ³Mental Health Institute – Hospital del Mar (Parc de Salut Mar), Psychiatric Hospitalization Programme, Barcelona, Spain, ⁴Mental Health Institute – Psychiatric Hospitalization Programme, Hospital del Mar (Parc de Salut Mar), Barcelona, Spain

Background: Mechanical restraint remains a key marker of acute severity, behavioural risk and coercion in inpatient psychiatry; systematic reviews report clinically relevant physical and psychological adverse outcomes associated with restrictive practices and highlight substantial international variability, underscoring the need for real-world evidence on predictors and prevention strategies. [1,2] Evidence is particularly needed in dual diagnosis (co-occurring mental disorder and substance use disorder) populations, where clinical complexity and behavioural dysregulation may increase the probability of coercive measures.

Aims & Objectives: To estimate the prevalence of mechanical restraint during acute psychiatric admissions in a dual diagnosis inpatient cohort and to identify associated clinical risk markers, focusing on admission legal status (involuntary vs voluntary) and history of aggression.

Method: We conducted a retrospective observational study of 1,551 acute admission episodes involving patients with dual diagnosis, admitted to the dual diagnosis inpatient units of Centre Fòrum and Centre Dr. Emili Mira, both belonging to the Institut de Salut Mental, Hospital del Mar (Barcelona, Spain). The primary outcome was mechanical restraint during admission (yes/no). Candidate predictors were involuntary admission, history of aggression towards persons/objects, legal history, age at admission and sex. Associations were examined descriptively and using multivariable logistic regression, reporting adjusted odds ratios (aOR) with 95% confidence intervals (CI).

Results: Mechanical restraint occurred in 11.0% of admissions (171/1,551). Restraint was more frequent in involuntary compared with voluntary admissions (16.6% vs 1.6%) and among patients with a history of aggression (17.5% vs 6.3%). In the multivariable model, involuntary admission (aOR 9.99, 95% CI 5.04–19.80; p<0.001) and aggression history (aOR 2.56, 95% CI 1.74–3.77; p<0.001) were independently associated with restraint. Increasing age showed a modest inverse association with restraint (aOR 0.98 per year, 95% CI 0.96–0.99; p=0.004). Sex and legal history were not independently associated with restraint.

Discussion & Conclusions: In this dual diagnosis inpatient cohort from two specialised units within the Hospital del Mar mental health network, mechanical restraint affected approximately one in nine admissions and was strongly associated with involuntary admission and aggression history. These findings support structured early risk assessment and targeted prevention strategies (e.g., enhanced observation and de-escalation protocols) for high-probability subgroups. Future work should incorporate symptom severity, intoxication measures and organisational factors to refine prediction and evaluate prevention bundles.