Current efforts focus on the search for genes that influence underlying processes, such as threat appraisal or risk aversion, that may be common to more than one mental, emotional, or behavioral disorder. More recently, genetic approaches are also being used to map out the role of environmental factors in the etiology of MEB disorders in people with different genetic profiles; that is, the extent to which (1) a disorder occurs in the presence of a given risk factor only in those with a specific genetic trait or (2) genetic effects on environmental exposure increase risk of a disorder.

As discussed in Chapter 5, continued research may make it possible to identify and target the most genetically vulnerable children for prevention interventions. Also, identifying gene variants that are associated with MEB disorders may eventually lead to prevention approaches based on modifying components of the pathways from genes to behaviors. However, the focus of prevention for the foreseeable future will still be on psychosocial interventions that change environmental risk factors. Research on signature sets of risk factors suggests that it may also be possible to target prevention efforts for some disorders to youth with high levels of signature risk for that disorder, potentially including both environmental and genetic factors. There is also an argument to be made for paying attention to risk factors, like maternal depression or family disruption, that affect multiple types of MEB disorders (see Chapter 4).

There is, of course, no simple answer to this question. National surveys and databases can be helpful in monitoring some of the epidemiological factors thought to be associated with emotional or behavioral disorders. For example:

• Low birth weight and other perinatal hazards may be increasing in the United States because of the increasing number of births from in vitro fertilization, the increasing age of women at first birth, and other factors. The proportion of newborns under 2,500 grams rose by more than 20 percent between 1980 and 2005.³

• Family poverty fell in the 1990s but has been level since then (according to the 2000 U.S. census).

• Divorce rates have fallen since their peak in the 1980s (U.S. census).

• Single-parent households have risen steadily, especially since the 1970s (U.S. census).