This study seeks to investigate if hyponatraemia be a direct contributor to death in schizophrenic and bipolar patients, and gauge the potential role of somatic comorbidity and psychotropic polypharmacy, with emphasis on antipsychotics and antidepressants.

Source population:

• Danish residents
• At least one International Classification of Diseases version 10 (ICD-10) F2 or F31 diagnosis from a hospital in Region Zealand and the Capital Region (Denmark)

No exclusion criteria.

Cases:

• Died in our catchment area between 1 January 2011 and 1 July 2016.

Controls:

• 5 controls per case found by risk-set sampling with replacement, matched on date of birth +/- 180 days.

We are unfortunately unable to share individual participant data, as our data source comprises sensitive information from electronic medical records and national registries.