Who do we need to study?
Several subgroups of patients have typically been excluded from treatment research. In particular, patients with coexisting Axis I disorders are routinely excluded from many treatment studies because of the complications concerning the management of separate conditions. However, the National Comorbidity Survey27 has shown that depression often co-occurs with many other disorders, including substance abuse, psychosis, and anxiety disorders. Although past studies have included patients with comorbid symptoms of substance use and anxiety, little is known about the impact these interventions have when full-blown comorbid disorders are present.
Samples included in recent studies of depression treatment are becoming more diverse with respect to age and minority representation. However, little is known regarding the specific response to treatment in these populations or how response rates compare with those found with more traditional study populations. This is important work to undertake, given that certain age and minority groups have been found to have varying responses to existing treatments. For example, given the pharmacokinetic complications that have been associated with antidepressant medications in ethnic minority populations, investigating the effectiveness of existing interventions in these populations is also important.13
Along similar lines, preliminary research suggests that older people take longer to respond to antidepressant therapies and require smaller doses to prevent toxic effects.4 Other age groups, such as children and adolescents are rarely studied, though this may change as the result of new National Institutes of Health guidelines on the inclusion of children as research subjects. Also, people seeking treatment in medical organizations other than primary care medicine or psychiatry have not been systematically studied. For example, the rates for depression in women seen in obstetrics/gynecology are quite high, but there are no published treatment studies with this population.28 Finally, patients who live in areas where care is hard to access (ie, rural populations) are currently being studied with promising results, yet to date there are no published outcomes.
Conclusions
The current literature shows that depression can be treated in many patients, but treatment response largely depends on the chronicity of the illness and the level of psychosocial stress faced by the patient. Future research should focus on how to best treat patients who tend not to respond to or accept existing treatment and should also examine the effectiveness of existing interventions for special populations who have not been included in past research. Thus far the evidence regarding the effectiveness of depression treatment is very promising, and the results of previous research will be useful in informing future work.