Overview of Prevention

The field of public health has long recognized the imperative of prevention to contain a major health problem (IOM, 1988). The principles of prevention were first applied to infectious diseases in the form of mass vaccination, water safety, and other forms of public hygiene. As successes amassed, prevention came to be applied to other areas of health, including chronic diseases (IOM, 1994a). A landmark report published by the Institute of Medicine in 1994 extended the concept of prevention to mental disorders (IOM, 1994a). Reducing Risks for Mental Disorders evaluated the body of research on the prevention of mental disorders, offered new definitions of prevention, and provided recommendations on Federal policies and programs, among other goals.

Preventing an illness from occurring is inherently better than having to treat the illness after its onset. In many areas of health, increased understanding of etiology and the role of risk and protective factors in the onset of health problems has propelled prevention. In the mental health field, however, progress has been slow because of two fundamental and interrelated problems: for most major mental disorders, there is insufficient understanding about etiology and/or there is an inability to alter the known etiology of a particular disorder. While these have stymied the development of prevention interventions, some successful strategies have emerged in the absence of a full understanding of etiology.

Rigorous scientific trials have documented successful prevention programs in such areas as dysthymia and major depressive disorder (Munoz et al., 1987; Clarke et al., 1995), conduct problems (Berrento-Clement et al., 1984), and risky behaviors leading to HIV infection (Kalichman et al., in press) and low birthweight babies (Olds et al., 1986). Much progress also has been made to prevent the occurrence of lead poisoning, which, if unchecked, can lead to serious and persistent cognitive deficits in children (Centers for Disease Control and Prevention, 1991; Pirkle et al., 1994). Lastly, historical milestones in prevention of mental illness led to the successful eradication of neurosyphilis, pellagra, and measles encephalomyelitis (measles invasion of the brain) in the developed world.

Definitions of Prevention

The term “prevention” has different meanings to different people. It also has different meanings to different fields of health. The classic definitions used in public health distinguish between primary prevention, secondary prevention, and tertiary prevention (Commission on Chronic Illness, 1957). Primary prevention is the prevention of a disease before it occurs; secondary prevention is the prevention of recurrences or exacerbations of a disease that already has been diagnosed; and tertiary prevention is the reduction in the amount of disability caused by a disease to achieve the highest level of function.

The Institute of Medicine report on prevention identified problems in applying these definitions to the mental health field (IOM, 1994a). The problems stemmed mostly from the difficulty of diagnosing mental disorders and from shifts in the definitions of mental disorders over time (see Diagnosis of Mental Illness). Consequently, the Institute of Medicine redefined prevention for the mental health field in terms of three core activities: prevention, treatment, and maintenance (IOM, 1994a). Prevention, according to the IOM report, is similar to the classic concept of primary prevention from public health; it refers to interventions to ward off the initial onset of a mental disorder. Treatment refers to the identification of individuals with mental disorders and the standard treatment for those disorders, which includes interventions to reduce the likelihood of future co-occurring disorders. And maintenance refers to interventions that are oriented to reduce relapse and recurrence and to provide rehabilitation. (Maintenance incorporates what the public health field traditionally defines as some forms of secondary and all forms of tertiary prevention.)

The Institute of Medicine’s new definitions of prevention have been very important in conceptualizing the nature of prevention activities for mental disorders; however, the terms have not yet been universally adopted by mental health researchers. As a result, this report strives to use the terms employed by the researchers themselves. To avoid confusion, the report furnishes the relevant definition along with study descriptions.

When the term “prevention” is used in this report without a qualifying term, it refers to the prevention of the initial onset of a mental disorder or emotional or behavioral problem, including prevention of comorbidity. First onset corresponds to the initial point in time when an individual’s mental health problems meet the full criteria for a diagnosis of a mental disorder.

Risk Factors and Protective Factors

The concepts of risk and protective factors, risk reduction, and enhancement of protective factors (also sometimes referred to as fostering resilience) are central to most empirically based prevention programs. Risk factors are those characteristics, variables, or hazards that, if present for a given individual, make it more likely that this individual, rather than someone selected at random from the general population, will develop a disorder (Garmezy, 1983; Werner & Smith, 1992; IOM, 1994a). To qualify as a risk factor the variable must antedate the onset of the disorder. Yet risk factors are not static. They can change in relation to a developmental phase or a new stressor in one’s life, and they can reside within the individual, family, community, or institutions. Some risks such as gender and family history are fixed; that is, they are not malleable to change. Other risk factors such as lack of social support, inability to read, and exposure to bullying can be altered by strategic and potent interventions (Coie & Krehbiel, 1984; Silverman, 1988; Olweus, 1991; Kellam & Rebok, 1992). Current research is focusing on the interplay between biological risk factors and psychosocial risk factors and how they can be modified. As explained earlier, even with a highly heritable condition such as schizophrenia, concordance studies show that in over half of identical twins, the second twin does not have schizophrenia. This suggests the possibility of modifying the environment to eventually prevent the biological risk factor (i.e., the unidentified genes that contribute to schizophrenia) from being expressed.

Prevention not only focuses on the risks associated with a particular illness or problem but also on protective factors. Protective factors improve a person’s response to some environmental hazard resulting in an adaptive outcome (Rutter, 1979). Such factors, which can reside with the individual or within the family or community, do not necessarily foster normal development in the absence of risk factors, but they may make an appreciable difference on the influence exerted by risk factors (IOM, 1994a). There is much to be learned in the mental health field about the role of protective factors across the life span and within families as well as individuals. The potential for altering these factors in intervention studies is enormous. The construct of “resilience” is related to the concept of protective factors, but it focuses more on the ability of a single individual to withstand chronic stress or recover from traumatic life events. There are many different perceptions of what constitutes resilience or “competence,” another related term. Despite the increasing popularity of these ideas,“virtually no intervention studies have been conducted that test the outcomes of resilience variables” (Grover, 1998).

Preventive researchers use risk status to identify populations for intervention, and then they target risk factors that are thought to be causal and malleable and target protective factors that are to be enhanced. If the interventions are successful, the amount of risk decreases, protective factors increase, and the likelihood of onset of the potential problem also decreases. The risks for onset of a disorder are likely to be somewhat different from the risks involved in relapse of a previously diagnosed condition. This is an important distinction because at-risk terminology is used throughout the mental health intervention spectrum. The optimal treatment protocol for an individual with a serious mental condition aims to reduce the length of time the disorder exists, halt a progression of severity, and halt the recurrence of the original disorder, or if not possible, to increase the length of time between episodes (IOM, 1994a). To do this requires an assessment of the individual’s specific risks for recurrence.

Many mental health problems, especially in childhood, share some of the same risk factors for initial onset, so targeting those factors can result in positive outcomes in multiple areas. Risk factors that are common to many disorders include individual factors such as neurophysiological deficits, difficult temperament, chronic physical illness, and below-average intelligence; family factors such as severe marital discord, social disadvantage, overcrowding or large family size, paternal criminality, maternal mental disorder, and admission into foster care; and community factors such as living in an area with a high rate of disorganization and inadequate schools (IOM, 1994a). Also, some individual risk factors can lead to a state of vulnerability in which other risk factors may have more effect. For example, low birthweight is a general risk factor for multiple physical and mental outcomes; however, when it is combined with a high-risk social environment, it more consistently has poorer outcomes (McGauhey et al., 1991). The accumulation of risk factors usually increases the likelihood of onset of disorder, but the presence of protective factors can attenuate this to varying degrees.

The concept of accumulation of risks in pathways that accentuate other risks has led prevention researchers to the concept of “breaking the chain at its weakest links” (Robins, 1970; IOM, 1994a). In other words, some of the risks, even though they contribute significantly to onset, may be less malleable than others to intervention. The preventive strategy is to change the risks that are most easily and quickly amenable to intervention. For example, it may be easier to prevent a child from being disruptive and isolated from peers by altering his or her classroom environment and increasing academic achievement than it is to change the home environment where there is severe marital discord and substance abuse.

Because mental health is so intrinsically related to all other aspects of health, it is imperative when providing preventive interventions to consider the interactions of risk and protective factors, etiological links across domains, and multiple outcomes. For example, chronic illness, unemployment, substance abuse, and being the victim of violence can be risk factors or mediating variables for the onset of mental health problems (Kaplan et al., 1987). Yet some of the same factors also can be related to the consequences of mental health problems (e.g., depression may lead to substance abuse, which in turn may lead to lung or liver cancer).