This study examined, first, effectiveness of a brief behavioural activation treatment for depression, in which participants engaged concurrently in activities of various difficulty instead of a standard least-to-most difficult sequence; and second, the relationship between behavioural self-observations of changes in activity levels and depressive symptomatology. Two adults with mild to moderate BDI-II depressive symptoms participated in a with-in participant multiple baseline study that contained 8 weekly conjoint sessions. Results showed that depression decreased to minimal levels at posttreatment and 1-month follow-up as a function of increases in activities of various difficulty. Results suggest early initiation of more difficult activities, and corroborate the relationship between increased activities and decreased depressive symptoms.
