Has time come for broad-scale dissemination for prevention of depressive disorders?

It has long been thought that it is not possible to prevent the onset of mental disorders such as depression, because the processes involved in the etiology are too complex and not yet sufficiently understood. However, in the past 15 years, the knowledge about identifying target groups for prevention and about the effects of preventive interventions has increased considerably. In the 1990s the first studies were conducted which examined the effects of preventive interventions on the incidence of depressive disorders in people who did not meet diagnostic criteria for a depressive disorder (1, 2). In a recent meta-analytic review, we found 19 studies examining the effects of preventive interventions on the incidence of depression (3). This meta-analysis demonstrated that preventive interventions reduce the incidence of depressive disorders with 22% compared with control groups who did not receive the interventions. This is a statistically significant finding (P < 0.01), which supports the idea that preventive interventions are actually capable of preventing the onset of depressive disorders in some cases. Most researchers and practitioners define prevention as interventions that are conducted before people meet the criteria of a depressive disorder according to the DSM-IV (4). Three types of prevention can be discerned: universal prevention, which is aimed at the general population or parts of the general population, regardless of whether they are at elevated risk of developing a disorder (e.g. school programs or mass media campaigns); selective prevention which is aimed at high-risk groups, who have not yet developed a mental disorder; and indicated prevention which is aimed at individuals who have some symptoms of a mental disorder but do not meet diagnostic criteria. In our meta-analysis we found no indication that universal prevention was effective in reducing the incidence of depressive disorders. We did find indications that prevention, directed at people presenting with subthreshold depression is effective. It could be argued that indicated prevention may not be actual prevention at all, because these symptoms could be a part of the prodromal phase of the disorder, and prevention is in fact early intervention in such cases, intervening in a process which has already started. However, our metaanalysis showed that selective prevention is also effective, suggesting that prevention of new cases is indeed possible. To be more specific, these preventive interventions are aimed at high-risk groups, such as pregnant women and general medical patients (5). Although preventive interventions have been found to be effective in reducing the incidence of depressive disorders, more research in this area is clearly needed. One important challenge for future research is to improve the interventions efficacy. In our meta-analysis, we found that preventive interventions reduce the incidence rate with 22%. We found some indications that interventions based on interpersonal psychotherapy may result in greater reductions in incidence. Another possibility to improve efficacy is to use stepped-care approaches in indicated preventive interventions (6). When someone has a subthreshold depression, it seems logical to monitor these symptoms regularly and when they do not improve, a non-intrusive intervention seems to be the best option. If such an intervention is not sufficient to ameliorate the symptoms, a more intensive intervention should be used, and when that fails, full pharmacological and psychological treatment can be applied. A series of trials examining the possibility of stepped care in prevention has recently started (6) and the outcomes are impressive. Another area where future research is necessary, concerns defining the best target populations for preventive interventions. Methods to identify the most optimal target populations for prevention have been developed recently (7–9). In this line of research, epidemiological cohort data can be used to identify those target groups in which a maximum health gain can be generated against a minimal effort. To illustrate, it was shown in one study that older adults with subthreshold depression, functional limitations, a small social network and a female gender comprise only 8% of the total population, while 25% of the total number of Acta Psychiatr Scand 2008: 118: 419–420 All rights reserved DOI: 10.1111/j.1600-0447.2008.01294.x Copyright 2008 The Authors Journal Compilation 2008 Blackwell Munksgaard