Depressive disorders are present in about 10% of primary care patients and account for more years lived with disability than any single disease. 1,2 Nearly three-quarters of all outpatient visits for depression are to primary care clinicians rather than to mental health specialists. 3 Collaborative care is a therapeutic intervention in which behavioral health is integrated into primary care, most commonly using a nurse care manager to monitor depressive symptoms in depressed patients and adjust treatment under the supervision of a psychiatrist. Many of the nurse contacts are conducted by telephone, thereby increasing the efficiency of collaborative care. Although collaborative care has been demonstrated to improve depression in more than 80 randomized clinical trials, 4,5 most trials have targeted major depression.Major depression requires the presence of at least 5 of 9 criterion symptoms of depression for 2 weeks or longer, with at least 1 of the symptoms being depressed mood or anhedonia. 6 In comparison, subthreshold depression (also called minor or subsyndromal depression) is the presence of 2 to 4 criterion symptoms of depression for 2 weeks or longer with at least 1 of the core symptoms (depressed mood or anhedonia). 6,7 Alternative definitions of subthreshold depression use a severity cut point on a depression scale or vary in duration and core symptom requirements but typically require the absence of major depression. Only a small number of therapeutic trials have targeted subthreshold depression, and results have been mixed. 6,8 Identifying effective therapies for subthreshold depression is important because many patients with subthreshold depression have persistent depressive symptoms at 12-month follow-up, a third to half report moderate functional impairment, and at least 10% to 20% progress to major depression. 6,7,9,10 In this issue of JAMA, the CASPER trial by Gilbody et al 11 provides the first evidence that collaborative care may benefit patients with subthreshold depression. In this pragmatic clinical trial conducted in the United Kingdom, the authors randomized 705 adults aged 65 years or older with subthreshold depression to either a collaborative care intervention or usual primary care. The collaborative care treatment consisted of 8 weekly 30-minute sessions of behavioral activation administered by a care manager with a background in mental health nursing or psychology who was supervised by a mental health professional. Behavioral activation is a psychological intervention that encourages increased social interactions and engagement in pleasur-Editorial Opinion