et al. (1998) conducted a 12-week RCT that involved the administration of sertraline or imipramine, in which the most notable predictors of treatment response were educational attainment and relationship status; in addition, the authors noted the apparent influence of intrinsic personal traits. However, Hirschfield et al. noted the limitation of a lack of a placebo control. Klein, Taylor, Harding, and Dickstein (1988) reported that, via their assessment of clinical, familial, and socio-environmental characteristics of those with chronic depression, at a six-month follow-up, individuals with double depression experienced decreased rates of remission, increased manifestations of clinical depressive phenomena, increased functional impairment, and increased likelihood of the development and onset of a hypomanic episode than their MDD-alone counterparts; as a result, the authors underscore the importance of the creation of a distinct classification of double depression due to its unique episodic path. Controversies Previous research on the clinical presentation of double depression tends to be mixed. Numerous studies indicate that the course of double depression tends to be more severe in nature. In addition, numerous studies demonstrate that individuals with double depression seek medical attention to a more substantial extent than those with either MDD or PDD. However, Miller, Norman, and Dow (1986) determined that individuals with MDD or PDD versus individuals with double depression experienced similar levels of social impairment. In addition, McCullough and colleagues found that there were few additional differences overall between the characteristics of those with double depression versus those with either MDD or PDD. Research on the course of double depression is also mixed. Klein, Taylor, Harding, and Dickstein (1988) found that remission in individuals with double depression is less probable than it is in individuals with either MDD or PDD; the researchers also noted that those with double depression are more prone to the development and onset of a hypomanic episode than those with either MDD or PDD. In addition, Klein, Shankman, and Rose (2008) and Hirschfield et al. (1998) both concluded that educational status predicted treatment outcome. However, Levitt, Joffe, and MacDonald (1991) demonstrated that the courses of the respective depressive disorders did not differ to a substantial extent. While Klein, Shankman, and Rose (2008) advocate for the creation of a distinct classification of double depression in the future edition(s) of the DSM, Levitt and colleagues (as well as McCullough and colleagues) seem to indicate that, due to the numerous similarities as well as limited