Mood is what the patient tells you they feel. Affect is what you observe they feel. They often disagree — and the disagreement is the data. Documenting them separately is one of the most useful disciplines in the MSE.
Mood is reported. Ask the patient directly: "How would you describe your mood?" Use their own words. "Down." "Numb." "Fine." "Irritable." "Anxious." The patient's exact word is data; the clinical translation often loses signal. A 0-10 scale can be useful — "On a scale of 0 to 10, where 0 is the worst you've ever felt and 10 is your best, where are you today?"
Affect is observed. Document on specific dimensions: range (constricted, normal, expanded), intensity (blunted, normal, exaggerated), congruence (with stated mood, with content), stability (stable through the encounter or labile), reactivity (does the patient brighten with humor or remain unchanged?). "Affect: constricted range, reduced intensity, congruent with stated dysphoric mood, minimally reactive to humor."
Congruence is the diagnostic gold. When mood and affect match — depressed mood with dysphoric affect, anxious mood with anxious affect — the picture is straightforward. When they don't, ask why. Patient reports "fine" while presenting with constricted affect, tearful, recently bereaved — limited insight, perhaps depression with avoidance, perhaps cultural display rules. Patient describes deeply traumatic content with flat affect — possibly dissociation, possibly severe defensiveness. Patient laughs while describing serious suicidal ideation — concerning, raises questions about thought content and disconnection.
The constricted affect of severe depression deserves specific recognition. The patient who reports feeling "okay" but has limited facial expression, monotone voice, reduced gesturing, minimal emotional reactivity — this is constricted affect, and it can mask depression that the verbal report minimizes. Family corroboration often confirms the picture.
Avoid interpretation-as-observation. "Anxious affect" is conclusion. What you saw was "fidgety motor activity, increased respiratory rate, sweating, tense posture" — that's the observation that supported the conclusion. Document the observation; let the next reader weigh the interpretation.