Depression Severity, Response, and Remission Outcomes

Definition and scope

Distinct outcomes for symptom level, symptom change, response, and remission under a specified depression instrument and follow-up rule, rather than an interchangeable set of diagnosis-code labels. The target population, use, and analysis remain protocol decisions; this card explains the choices and their consequences rather than approving a study.

Operational specification

Specify instrument/version, reporter, item and total scoring, recall, baseline severity, follow-up window, response and remission rules, missing-item handling, and repeat confirmation if required. A PHQ-9 score is not identical to a structured diagnostic interview, and a threshold-based definition is not automatically transportable to every language, population, or mode.

Analysis and diagnostics

Retain continuous scores and evaluate floor/ceiling effects, baseline adjustment, repeated measurements, and informative assessment. Report denominator and missingness for threshold-based outcomes. Separate remission at a visit from sustained remission and relapse after remission, each of which needs its own observation window and eligibility.

When NOT to use and common errors

Do not infer remission from disappearance of a billing code or antidepressant discontinuation, count unassessed patients as symptom-free, or choose a response threshold after seeing the treatment difference. Instrument-level validation does not prove a particular causal comparison.

Worked example and implementation boundary

A synthetic PHQ-9 trajectory goes from 18 to 9 under a specified assessment schedule. Calculate relative symptom-score reduction; whether it is the study's response definition must be stated separately. The score reduction is 0.50, or 50%. This alone does not establish sustained remission or diagnose an individual. The code performs that explicitly stated calculation with synthetic inputs. It is not a complete fitted analysis and does not demonstrate the identification assumptions, estimate sampling uncertainty, or certify application in another population.

Data-source and reporting requirements

Preserve the provenance, dates, units, and observation rule for each input. Claims capture services and transactions under observable benefits; absence of a record is not proof that an event or resource use did not occur. EHR and registry measurements depend on the collection process and may miss care outside the system. Linked sources add reconciliation and selection questions. Primary collection can improve a missing domain but still requires valid measurement and follow-up. Report which of these limitations affects the stated use, which evidence supports the chosen inputs, and what remains uncertain.

Worked example

Scenario

A synthetic PHQ-9 trajectory goes from 18 to 9 under a specified assessment schedule. Calculate relative symptom-score reduction; whether it is the study's response definition must be stated separately.

Dataset

Synthetic inputs with units defined in the scenario; no patient data.

Steps

Result

The score reduction is 0.50, or 50%. This alone does not establish sustained remission or diagnose an individual.

Trade-offs

Code example

baseline = 18
followup = 9
result = (baseline-followup)/baseline
assert abs(result - 0.5) < 1e-9
print(result)

baseline <- 18
followup <- 9
result <- (baseline-followup)/baseline
stopifnot(abs(result - 0.5) < 1e-9)
print(result)

data worked_example;
  baseline = 18;
  followup = 9;
  result = (baseline-followup)/baseline;
  put result=;
run;

Citations

1. [1]Kroenke K, et al. The PHQ-9. Journal of General Internal Medicine. 2001.
2. [2]U.S. Food and Drug Administration. Patient-Focused Drug Development: Selecting, Developing, or Modifying Fit-for-Purpose Clinical Outcome Assessments. Final guidance. October 2025.