"Tapping the Mood Gene"

What's the key to happiness? A quick glance of news headlines in 2003 would lead us to a simple answer: genetics. A study of young adults' depression was published in Science, and its findings were quickly picked up by the national media, who proclaimed that "Scientists Find Depression Gene" (BBC News 2003), "Vulnerability to Depression May Lie in Your DNA" (Doheny 2003), and "Gene Is Linked to Susceptibility to Depression" (Duenwald 2003). A closer inspection of the Science study, conducted by King's College psychologist Avshalom Caspi and his collaborators (2003), reveals that it takes more than just DNA to make someone depressed. Rather, both nature (or genetics) and nurture (social environment) affect our mental health.

Caspi and colleagues set out to investigate the ways that genes and stressful life events affect the chances that a young adult experiences depression and suicidal thoughts. The researchers focused on a cohort of 847 whites in New Zealand who were born in the early 1970s. They collected data on the cohort from birth through age twenty-six. These data included information on their families, economic resources, health, and the stressful experiences they encountered between the ages of twenty-one and twenty-six—such as parental divorce, school failure, economic troubles, and breaking up with a boyfriend or girlfriend. The study also obtained data on genetic factors. Specifically, the researchers measured which type of 5-HTT gene one had. The 5-HTT gene controls the ways that serotonin passes messages through brain cells, and it is considered a gene that may affect depression. The three possible 5-HTT gene varieties, or genotypes, were: two copies of a short allele, two copies of a long allele, and one short and one long allele. (An allele is a pair or series of genes.)

Three important findings emerged from the study. First, the more stressful events a young person experienced, the more likely that person was to become depressed. For example, those who experienced four or more stressful life events were nearly four times as likely to experience depression, compared to those who experienced no stressful events. Second, the researchers found no statistical association between the type of 5-HTT gene one had and that person's chances of being depressed. If genes had no effect on depression, how could reporters claim that a "depression gene" exists?

Although the scientists did not find a direct effect of genes on depression, they did find evidence of an "interaction effect." That means that the influence of one variable (such as stress) on depression is contingent upon a second variable (such as genetics). Specifically, the researchers found that the effects of life stress on depression were most severe for those young people who had a particular genetic makeup. Of the 15 percent of young people who had experienced four or more stressful life events, 33 percent of those who had a short allele became depressed—compared to just 17 percent of those who had two long alleles. Overall, these findings reveal that "nature" alone does not cause depression, but the interplay of both "nature" and "nurture" affects young people's chances of becoming depressed.

The media underplayed the importance of stressful life events yet overstated the influence of genes on depression. Rutgers University sociologist Allan Horwitz (2004) has argued that media attention on genetics draws attention away from important social influences on mental health. For example, many of the stressful life events considered in the study are events that are particularly common among economically disadvantaged young people, such as losing a job, being in debt, and having difficulty paying bills or covering medical expenses. By focusing on genetics only, the media and the scientific community may send the message that depression among young people can and should be treated through medications. However, Horwitz counters that an equally valuable strategy is to develop policies and practices that would help to reduce social inequalities and the stressors associated with these inequalities.

The media's portrayal of Caspi's study and Horwitz's critique of the media attention illustrate a key theme of "the sociological imagination." Sociologist C. Wright Mills claimed that the goal of sociology is to show how seemingly personal problems, like depression, may reflect underlying "public issues." The media's attention to individuals' genetic makeup, rather than to social context, suggests that Mills's message still has not been heard or heeded by all.