Sustained Mood Improvement With Laughing Gas Exposure

Change in Montgomery-Åsberg Depression Rating Scale (MADRS) score

The MADRS is a 10-item clinician-rated scale used to assess the severity of depressive symptoms and to detect changes over time in response to treatment. It is commonly used in randomized controlled trials due to its sensitivity to change and strong psychometric properties. The MADRS is also recognized by regulatory and health technology assessment agencies, including the U.S. Food and Drug Administration (FDA) and the Canadian Agency for Drugs and Technologies in Health (CADTH), as an established measure for evaluating treatment efficacy in depression. Higher scores indicate worse outcomes and greater severity of depression.

Proportion of patients who achieved a response

Defined as a 50% reduction in MADRS score between baseline and the 2- and 12-week follow-ups.

Proportion of patients who achieved remission

Defined as achieving both a response and a MADRS score \<10 at the 2- and 12-week follow-ups.

Change in self-reported depressive symptoms

Quick Inventory of Depressive Symptomatology - Self-Report (QIDS-SR-16) Higher scores are associated with increased severity in depressive symptoms Total scores range from 0-27 Normal/No Depression 0-5 Mild Depression 6-10 Moderate Depression 11-15 Severe Depression 16-20 Very Severe Depression 21-27

Change in cognitive function

Assessed using the Digit Symbol Substitution Test (DSST) The Digit Symbol Substitution Test (DSST) measures processing speed, attention, and executive function by assessing a person's ability to quickly and accurately pair numbers with symbols according to a key. To score it, the total number of correct symbol-for-number substitutions completed within a timed period (typically 90-120 seconds) is counted. Higher scores indicate better performance.