Before we speculate further on international differences, we must also consider how expression of opinions and test-taking characteristics affect U.S. teens' responses to questionnaires, interviews and scales and in clinical histories. Communications of feelings, coping styles and other characteristics may vary in different nations and among adolescents. Many screening tests and measures of acute depressive symptoms (used during the last week in the WHO study) may not be good proxies for actual depressive disorders. Reports of depressive symptoms may reflect variations in stigmatization of mental disorders and concepts of health and well-being. Depression has different manifestations in children than it does in adults, and assessment scales often developed for adults tend to overestimate depression scores when applied to youth (Costello and Angold, 1988; Roberts et al., 1991).
Finally, it is important to consider what significance subclinical or minor depression has in terms of long-term outcomes. Most studies are conducted in patients with severe impairment and recruitment is often in clinical and referred samples. We are just learning to appreciate the dimensionality of depressive disorders--that it is most likely not a dichotomous yes/no, on/off proposition.
Course of Illness
Depressive symptoms must also be viewed in the long-term perspective. Analysis of data from the National Longitudinal Study of Adolescent Health--a representative survey of U.S. adolescents in grades 7 through 12 conducted in the school and home in the mid-90s (Bearman et al., 1997)--shows the difficulties of predicting the course of depressive symptoms (Rushton et al., 2002). Students completed a version of the Center for Epidemiological Studies Depression (CES-D) Scale at the beginning of the study and one year later (Rushton et al., 2002). The majority of adolescents with minimal depressive symptoms (CES-D <16) at baseline continued to maintain similar CES-D scores a year later--only 3% of the group with minimal depressive symptoms developed moderate/severe depressive symptoms at one-year follow-up. For adolescents who were depressed at baseline, however, predicting persistent depressive features and resolution of symptoms proved very challenging. Many adolescents with moderate/severe symptoms reported a similar level of depression a year later, but more than half of the adolescents with moderate/severe depressive symptoms at baseline reported significant reduction on follow-up. Therefore, a negative screen on the CES-D or another evaluation of depressive symptoms may provide reassurance and place adolescents at low risk for future depressive symptoms. Adolescents with depressive symptoms may require ongoing evaluation though, since the course of their symptomatology can be quite variable.
In other analyses from our study, gender was the only sociodemographic variable consistently associated both with higher prevalence of depressive symptoms at baseline and follow-up.
Race, age and socioeconomic status were associated with higher baseline CES-D scores but did not predict greater likelihood of persistently elevated CES-D scores in longitudinal analysis. Other factors of adolescent self-esteem, resiliency, family and social support were not significantly associated with depressive symptoms.
Even with some knowledge of epidemiology, individual differences can be powerful and may limit the usefulness of risk factors and prediction strategies. We cannot forget the individual patient, comorbid conditions, and the family and social context. Depression is often a chronic, relapsing and recurrent disorder that must be approached with vigilance--no matter where an adolescent resides or their nationality, culture or race.
Yet, we cannot ignore the potential issues and comments on our society and modern life in the United States that are raised by reports that up to half of U.S. adolescents exhibit depressive symptoms. We must monitor rates of depression, particularly in this vulnerable group as they make their transition to adulthood; and we must keep an eye on prevention and early intervention before higher costs, morbidity and mortality are realized in later years. We must maintain a global perspective to work together and borrow from each other's successes in facing this important part of adolescents' lives. Finally, we cannot overlook the importance of communicating with each family and patient as we attempt to improve care of this complex chronic disorder and distinguish symptoms from disease.
Given the recent attention of genetics, neuroimaging, pharmacotherapy, public health and improved counseling techniques, we have multiple opportunities to improve care and impact entire nations, populations and individuals. Improvements may be realized through multiple approaches--targeted screening, probing with open communication and maintaining a high index of suspicion of possible depression in teens with school, family and/or social problems. Most important given the complex chronic course of depressive disorders and high occurrence of comorbid conditions, the first step may be to more effectively treat adolescents who are diagnosed with depression. The health care system must use innovations in information systems along with culturally sensitive, community-centered outreach initiatives to provide the long-term care and follow-up needed to prevent relapse and recurrence. Although national characteristics, cultural norms and other high-risk groups may inform the process and broaden research strategies, ultimately, clinical management must be individualized to the patient.