A recent review on the prevention of depression was featured in the May issue of the American Psychologist. The study authors (Munoz, Beardslee and Laykin) were decidedly positive in their appraisal of current prevention efforts. As the authors point out, prior to the 1980’s, it was the official position of the mental health gods that depression was not preventable. The last two decades have seen a reversal of this thinking. Psychologists from around the world have researched programs designed to prevent depression in the general population. Most of the prevention studies cited by these and other authors share many commonalities. First, the research subjects are randomly assigned to treatment and no-treatment groups. Second, the treatment group receives a course on the identification and reduction of depressive symptoms. The depression group intervention varies from a traditional lecture format to group therapy with an identified leader. Lastly, the prevention studies compare symptoms of depression at the beginning of the study with symptoms experienced at the end of the study. The authors then write a report summarizing their positive or negative findings.
Though their intent is certainly noble, the depression prevention researchers have encountered problems with methodology. The first problem is with the method to recruit and classify the study subjects. In order to lower the total number of subjects needed to complete the study, psychologists often use “at risk” individuals to populate the study. The term “at risk” has several meanings in the context of psychological research of this nature. A research subject may have experienced a prior depressive episode, there’s a family history of depression, they live in poverty, or the subject endorsed subclinical elevations on depression questionnaires. Subclinical refers to the manifestation of an abnormal number or type of symptom(s), yet they fail to meet the criteria of a known clinical condition. Unfortunately, the use of “at risk” people lessens the statistical power of the study. No longer are the study subjects randomly assigned to groups, but selected because of a particular trait. The psychologist cannot then compare the depression intervention to the general population, rather the comparison may only be drawn to other “at risk” groups.
Such group interventions may also fall prey to an old psychological phenomenon. Many years ago, psychologists who studied factory production noted consistent productivity gains across the length of the study. This phenomenon was titled the “Hawthorne Effect” after the name of the factory where it was initially observed. It was discovered that factory workers performed at a higher level when they were aware of being observed. After the study was terminated, the efficiency of the workers returned to the original lower level. Similarly, depression prevention subjects are aware of being observed and evaluated. Not only is there the Hawthorne Effect, and a normal bias to please the examiner, but mood is often elevated with the perception of special treatment. Sham groups may be utilized to counteract the natural biases and effects of being observed. A sham group is one where any subject may be discussed, with the exception of the issue being evaluated-depression in this particular case. The subjects attending the sham group may then be appropriately compared with groups that do discuss depression. The use of a sham group component will increase the power of the study. It will help differentiate whether a drop in the incidence of depression between groups is due to talking and lecturing about depression, or whether being observed and receiving special treatment accounted for the reduced prevalence of depressive symptoms.
It is certainly the author’s hope that depression is at least partially preventable. Many of the current interventions in use may be valuable, but the present design of these studies limits the power to draw accurate conclusions. Larger study sizes, that are truly randomized, should be combined with sham group interventions. Until there is an increased mindfulness of proper investigatory techniques, the current depression prevention results are not convincing. Stated another way, the correct prevention techniques may already exist, but hard evidence of their effectiveness is lacking. Let us all hope that psychological researchers discover effective methods to prevent depression, as it would not only benefit commerce, but our everyday social experience as well.