Low positive emotion distinguishes depression from most types of anxiety. Formative work in this area employed the Anhedonic Depression scale from the Mood and Anxiety Symptom Questionnaire (MASQ-AD), and the MASQ-AD has since become a popular measure of positive emotion, often used independently of the full MASQ. However, two key assumptions about the MASQ-AD—that it should be represented by a total scale score, and that it measures time-variant experiences—have not been adequately tested. The present study factor analyzed MASQ-AD data collected annually over 3 years (n = 618, mean age = 17 years at baseline), and then decomposed its stable and unstable components. The results suggested the data were best represented by a hierarchical structure, and that less than one quarter of the variance in the general factor fluctuated over time. The implications for interpreting past findings from the MASQ-AD, and for conducting future research with the scale, are discussed.