This study examined the effects of depression and cognitive impairment on the Medicare beneficiaries' plans to enroll in Medicare Part D and their enrollment status.  The authors found that vulnerable Medicare beneficiaries with depression or cognitive impairment had equal access to Medicare Part D enrollment with non-vulnerable beneficiaries; however, they note that additional research is needed to determine the extent to which Part D meets the needs of this population. 

Zivin, K., et al. (2009). The effect of depression and cognitive impairment on enrollment in Medicare Part D. Journal American Geriatric Society, 57(8): 1433-1440. http://www.ncbi.nlm.nih.gov/pubmed/19515100 

Authors: Kara Zivin, Mohammed U. Kabeto, Helen C. Kales, Kenneth M. Langa