Introduction- What is Locus of Control?
Originally developed within the framework of Rotter's (1954) social learning theory, the locus of control construct refers to the degree to which an individual believes the occurrence of reinforcements is contingent on his or her own behavior. The factors involved with reinforcement expectancy are labeled "external" and "internal" control. In short, internal locus of control refers to the perception of positive or negative events as being a consequence of one's own actions and thereby under one's own personal control. In contrast, external locus of control refers to the perception of positive or negative events as being unrelated to one's own behavior in certain situations and thereby beyond personal control. As a general principle, the locus of control variable may be thought of as affecting behavior as a function of expectancy and reinforcement within a specific situation (Carlise-Frank, 1991).
The following sections will review the evidence supporting links between locus of control and specific cardiovascular health-related behaviors. In addition, methods of assessment of locus of control will be discussed, as well as the current limitations of studies investigating the relationship between locus of control and cardiovascular health-related behavior.
How is Locus of Control Assessed in Health-Related Research?
Rotter's Locus of Control Scale (Rotter, 1966), a generalized measure of internal vs. external locus of control, continues to be widely used to assess perceived control in health-related research (see reviews by Strickland, 1978; Wallston and Wallston, 1978). However, many health researchers have chosen to use more situation-specific, health-related locus of control measures in their investigations. The most widely used instrument of this sort is the Multidimensional Health Locus of Control (MHLC) Scale (Wallston et al., 1978). The MHLC Scale consists of two alternative forms (A and B) each of which contains 18 items. Each form, in turn, contains three six-item Likert scales which, in "normal healthy" populations are uncorrelated, or only slightly correlated, with one another (Wallston and Wallston, 1981). The Internal Health Locus of Control (IHLC) dimension assesses the degree to which one believes one's health status is influenced by one's own behavior. People who score high on the IHLC are said to have a sense of responsibility for their own health (Wallston and Wallston, 1982). PHLC measures the belief that powerful other people (one's family, friends or health-care providers) control one's health. Lastly, CHLC assesses perceived non-control of health, or the belief that fate, luck, or chance determines ones health status. (Wallston, 1989)
Another approach to measuring locus of control are "Sphere-specific measures of perceived control" developed by Delroy Paulhus (1983). Paulhus' questionnaire has a total of 30 items, broken down into 3 subscales called "personal efficacy", "interpersonal control", and "socio-political control". The internal consistency reliabilities for the scales are typically .75-.80, higher than those obtained for the Potter scale on the same samples. Pauljus argues convincingly that the construct of locus of control is multidimensional, and that therefore a scale (such as his) that measures perceived control in different domains of life is a better measure than Rotter's single scale.
Locus of Control and Cardiovascular Health-Related Behaviors
The literature concerning research on the relationship between locus of control and health-facilitating behavior as a whole points toward internal locus of control as a mediating factor of actions taken to prevent health problems (See Lefcourt and Davidson-Katz, 1991; Carlise-Frank, 1991). Physical activity is one of these health-facilitating behaviors whose relationship to locus of control has been studied. Physical activity appears to decrease the risk of coronary artery disease. The United States Center for Disease Control reviewed existing observational studies and found a significant and graded relationship between physical activity and the risk of coronary artery disease
(Powell et al., 1987; Littman, 1993). Exercise is widely recommended for health promotion and primary-risk reduction in people who have not developed symptoms of cardiovascular illness (Ewart, 1995). However, relatively few people engage in regular exercise for a period of time to secure the benefits of moderate exercise to physical health (Duppert, 1992). The attrition rate for both clinical and community-based exercise programs can be as high as 50% within the first 3 to 6 months of participation (Brawley & Rogers, 1993; Dishman, 1988). Sonstroem and Walker (1973) studied locus of control and attitudes toward physical fitness and found that internals had more favorable attitudes towards physical activity, obtained significantly better fitness scores, and engaged in greater amounts of voluntary physical exercise than did externals (Carlise-Frank, 1991). It must be recognized, however, that these authors used a theoretical and methodological approach that supported a generalized expectancy for control beliefs. Validity of studies investigating the relationship between locus of control and health-related behaviors have been questioned due to the fact that an individual may have a tendency towards internality in many life areas, but have an external belief with regard to the particular health-related behavior in question. Please see the end of this section for further discussion of this methodological problem.
Like the research on health-facilitating behaviors, research on individuals who attempt to overcome health-damaging behaviors has also shown internals are often better off than externals (Coan, 1973; James et al., 1965; Mlott and Mlott, 1975; Naditch, 1975; Pryer and Distefano, 1977; Williams, 1967). Unlike research on health-facilitating behaviors, however, results of research on overcoming health-damaging behaviors has been far less consistent in favoring internality. In this area, results have shown that externals and internals are equally successful in overcoming their deleterious health behaviors when placed in treatment programs consistent with their personal control beliefs (Carlise-Frank, 1991).
Being overweight is a significant risk factor for the development of hypertension and coronary heart disease. In studies concerning weight reduction as a function of locus of control, Balch and Ross (1975) found internal beliefs to be predictive of success and completion of an overweight treatment program. (Carlise-Frank, 1991) (Wallston et al.1976), using the Health Locus of Control scale, found internals in weight reduction programs were more satisfied with the results of their treatment than externals, but these results failed to reach significance. "Some researchers have been unable to relate the internal/external (I-E) variable to weight reduction (Bellack et al., 1974; Manno and Marston, 1972; Tobias and MacDonalad, 1977)." (Carlise-Frank, 1991).
Cigarette smoking has also been identified as a risk factor for cardiovascular disease (Schnall et al., 1994). Furthermore, studies indicate that patients with coronary artery disease who stop smoking have a lower mortality from all causes of death and a less frequent occurrence of myocardial infarction in particular than those who continue to smoke (Vlieststra et al., 1986). Results from research on stopping smoking have shown that internals are far more likely than externals to be affected by the Surgeon General's report and are more likely to stop smoking (James et al., 1965). In another study, internals were found to profit more from a stop smoking program using a saturation technique than externals (Best and Steffy, 1975). Though some researchers have reported that internals are more likely to reduce their smoking rate than externals (Best and Steffy, 1971; Steffy et al., 1970), others have failed to demonstrate a relationship between locus of control and control of smoking behavior. In these studies, I-E scores have failed to predict treatment success, suggesting that locus of control data have little predictive value in smoking cessation (Berstein, 1970; Best and Steffy, 1971; Danaher, 1977; Keutzer, 1968; Carlise-Frank, 1991).
Perhaps one of the most important reasons for the discrepancy of studies investigating the relationship between locus of control and cardiovascular health-related behaviors is the approach used in determining whether individuals should be placed in internal or external treatment groups (Carlise-Frank, 1991). "The most commonly used measure of subjects' control beliefs has been a generalized unidimensional scale of overall expectancy. If an individual's belief system pointed towards internality, then he or she would be placed in a treatment regime consistent with that belief. However, an individual may have a tendency towards internality in many life areas but have an external belief with regard to health or the particular health-related behavior in question. It is unlikely that a generalized unidimensional scale would be able to detect such distinctions. If such individuals were placed in treatment groups congruent with internal beliefs, success might be marginal at best. From this perspective, internally oriented individuals who have learned externality or passive acceptance towards their health-damaging behavior would not be expected to have a high success rate in such programs."(Carlise-Frank, 1991). This would explain the failure by many researchers to demonstrate a relationship between locus of control as a predictor for overcoming the cardiovascular health-damaging behaviors previously discussed (Carlise-Frank, 1991).
Diagnosis of Myocardial Infarction, Recovery from Myocardial Infarction, and Locus of Control
Another area of investigation concerning locus of control and cardiovascular health involves how locus of control influences health-related behavior once myocardial infarction has already begun. Early detection of acute myocardial infarction(AMI) reduces myocardial infarction morbidity (Genton and Sobel, 1987), yet up to one third of AMIs are not recognized (Roseman, 1954; Lindberg et al., 1960; Roseman et al., 1967; Kannel and Abbott, 1984; Kannel et al., 1990). Unrecognized AMI includes completely asymptomatic events and those with a typical symptoms, so that neither the patient nor physician entertains the diagnosis of AMI (Bertolet and Hill, 1989). In a recent study by Theisen et al.(1995), patients with unrecognized AMI scored higher on the CHLC ("chance" locus of control) than patients with diagnosed AMI. Unrecognized AMI is known to result from a lack of symptom experience and/or avoidance of medical care when symptoms are experienced. In analysis of their results, Theisen et al.(1995) hypothesize that "chance" locus of control, the belief in chance or fate as determining health, may inhibit treatment-seeking for AMI. More research is needed to rigorously test this hypothesis (Theisen et al., 1995).
The role of locus of control in recovery from AMI has also been explored in a study by Cromwell et al. (1977). "Patients who were classified as internal from Rotter's Internal-External Locus of Control Scale (Rotter, 1966) were rated by the professional staff as being more cooperative and less depressed than were externals throughout their stay in the intensive care unit. On three highly intercorrelated physiological measures (sedimentation rates, serum glutamic oxaloacetic transaminase levels, and lactate dehydrogenase levels), externals were found to have worse prognoses than internals. Additionally, externals had higher peak temperatures during intensive care and remained longer in the unit, and in the hospital, than did internals. One tempting hypothesis is that internals simply behave in a manner that does not aggravate their fragile conditions. Rather than becoming distressed, with all of the personal and physiological consequences of distress, internals showed greater cooperation and less depression, possibly reflecting their more active participation and greater hope in the struggle for survival. It is plausible that responses to life-endangering threats such as myocardial infarction may be at least partially determined by personality characteristics such as locus of control."(Lefcourt and Davidson-Katz, 1991) However when a measure of control beliefs made up of items relating specifically to perceived control over recovery from heart disease was used, no support was found that perceived control is important for psychological adjustment among cardiac patients (Flowers, 1994). Further research is needed before an important evaluation of the hypothesis that an internal locus of control leads to increased likelihood of behavior favoring recovery from AMI.
Locus of Control and Job Strain
Karasek (1979) has defined "job strain" as work in jobs with high psychological demands and low control. In more than a dozen epidemiological studies over the last decade, occupational stress researchers have implicated job strain as a risk factor for heart disease (Schnall et al., 1994). Although the mechanism by which the stress of job strain influences development of CHD is unknown, previous findings suggest that job strain may be related to elevations of blood pressure at work (Schnall et al., 1990, Van Egeren, 1992). High blood pressure has long been known to be a marker for individuals at high risk for developing CHD, and therefore is one possible mechanism by which job strain might exert its deterious influences on the heart.
One basic question yet to be answered by the job strain model "relates to the issue of objective versus subjective control. Clearly, the job strain model considers control as an objective characteristic of the work situation. However, cognitive and affective responses of the workers to these characteristics vary considerably according to their individual patterns of appraisal and coping (Lazarus and Folkman, 1984). Generalized control beliefs have been found to moderate the effects of objective job conditions on well-being (Spector, 1987). Furthermore, through regression analysis, Hendrix (1989) found locus of control to be a statistically significant predictor of job stress (Beta=.39; p<.001). These findings (as well as findings where individual coping characteristics such as Type A behavior, hostility, or lack of hardiness were associated with increased ischemic heart disease) call for a conceptual clarification of the relationship between control-limiting job conditions and those personal characteristics (particularly locus of control) which influence the perception of control (Siegrist et al., 1990). One possible relationship is interaction between job conditions and personality characteristics. For example, Parkes (1991) found a significant three-way interaction between job demands, job decision latitude, and Paulhus' locus of control scale, in predicting affective distress and anxiety. For externals, demands and latitude combined intractively to predict outcome (consistent with Karasek's model), whereas for internals, additive findings (main effects for demands and latitude) were obtained.
Social determinants of Locus of Control
There has been remarkably little research on the determinants of locus of control, particularly social class and job control. Such factors might shape personality development in childhood. For example, certain parental behavior patterns (i.e., overly strict, critical and demanding of conformity) are more common in low SES households, and may be viewed as a reflection of the parents' occupational and other life experiences, which are characterized by low control and insecurity (Sennett and Cobb, 1973; Rubin, 1976). Similarly, an adult's experience, which might include stressful, low control jobs, may shape their personality development (Kohn and Schooler, 1982). For example, Lefcourt (1982, p. 31) pointed out that locus of control is "positively associated with access to opportunity"
In a study of 2174 Dutch men and women aged 25-74 (Bosma et al., 1998), subjects with higher chidlhood socioeconomic status (SES) had much higher levels of "perceived control" (locus of control) in adulthood. In addition, "perceived control" appeared to be an important mediatorof the association of SES with later mortality. The association between SES and mortality (RR=2.6) was reduced substantially (RR=1.8_ agter controlling for levels of "perceived control". Thus, research on the social determinants of personality measures believed to be associated with illness outcomes needs to be a major priority in future research.
Validity of studies investigating the relationship between locus of control and health-related behaviors have been questioned due to the fact that an individual may have a tendency to be internal in many life areas, but have an external belief with regard to the particular health-related behavior in question. Valid locus of control measures more specific to the particular behavior being studied need to be developed. However, results using Rotter's Locus of Control Scale and the more health behavior-related MHLC, have in general found that internals tend to behave in a more healthy way in regardseveral important cardiovascular health-related behaviors. Specifically,one study has shown internals to have better attitudes toward physical fitness, better physical fitness scores, and engaged in greater amounts of voluntary physical exercise (Sonstroem and Walker, 1973). Furthermore, there have also been findings suggesting that an internal locus of control may be beneficial in weight loss among the overweight, and successful smoking cessation. It should be noted however that there have been contradictory findings regarding the link between locus of control and these cardiovascular health-damaging behaviors. Another area of investigation concerning locus of control and cardiovascular health involves how locus of control influences health-related behavior once myocardial infarction has already begun. Patients with unrecognized AMI in one study were shown to score higher on the CHLC than patients with diagnosed AMI (Thiesen et al., 1995). This had led to the hypothesis that "chance" locus of control may inhibit treatment-seeking for AMI. Secondly, work by Cromwell et al. (1977) led to their hypothesis that an internal locus of control may lead to increased likelihood of behavior favoring recovery from AMI. There has been little further work investigating either of the aforementioned hypotheses. More research is definitely needed in these areas.
Locus of control may also be important in studies of job strain, implicated as a risk factor for heart disease by over a dozen epidemiological studies over the last decade. The current job strain model considers control as an objective characteristic of the work situation. Locus of control and other measures of generalized control beliefs have been shown to moderate the effects of objective job conditions on well being and as predictors of job stress. These findings call for future studies investigating the relationship between control-limiting job conditions and personal characteristics, such as locus of control, which influence the perception of control. Such work may lead to a better understanding of how the perception of control relates to job stress-related cardiovascular disease via the cardiovascular risk factor of job strain.
Lastly, there has been very little research on the determinants of locus of control. Research on the social determinants of personality measures believed to be associated with illness outcomes needs to be a major priority in future research.
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