How One Developer Built a Clinically Accurate Mental Health Screener for the Web

A developer building Ask.Dr, a free psychology self-assessment platform with over 240 tools, chose to implement only published, validated clinical instruments such as the PHQ-9 depression questionnaire rather than informal quizzes. The PHQ-9 uses a fixed 0–3 response scale across nine items, yielding a total score of 0–27 mapped to five severity bands from Minimal to Severe. The implementation enforces that all questions must be answered before a score is calculated, preventing skipped items from being silently treated as zero. Safety-flagged items — such as those related to self-harm — trigger a prominent warning displayed above the results, not hidden behind additional clicks. The project also follows strict disclosure rules, showing the instrument's citation, clarifying that results are not a diagnosis, and recommending professional consultation for moderate or higher scores.