Critical illness increases the risk of mental illness, including anxiety disorders. As critically ill patients exhibit high levels of inflammation and inflammation plays a role in mental illness, critical and mental illnesses may be linked by systemic inflammation.

To investigate whether anti-inflammatory drugs reduce the risk of subsequent anxiety disorders among intensive care patients requiring mechanical ventilation.

To assess the risk of anxiety disorders after intensive care requiring mechanical ventilation according to pre-admission use of non-steroidal anti-inflammatory drugs (NSAID), glucocorticoids, statins or combination. To compare risk in users with non-users.

This nationwide, registry-based, cohort study includes all patients receiving mechanical ventilation in Danish intensive care units during 2005–2013. Preadmission use of NSAIDs, glucocorticoids, statins or combinations will be identified from filled prescriptions. Risk of anxiety disorders in users and non-users of these anti-inflammatory drugs will be estimated using the cumulative incidence method, accounting for death as a competing risk. After propensity-score matching, risk in users and non-users will be compared using hazard ratios from a Cox regression.

N/A. The estimated number of patients is 100,000. Expected preadmission use is 14% for statins, 15% for NSAIDs, and 10% for glucocorticoids. The study will have 95% power to detect a 10% decrease in risk between users and non-users.

N/A. The study potentially will contribute knowledge about the pathogenesis of anxiety disorders and a mechanism linking critical illness and mental illnesses. If anti-inflammatory drugs reduce risk of anxiety disorders, this may guide trials.

The authors have not supplied their declaration of competing interest.