Neuroticism, or negative affectivity, is one of a small set of global traits that reflect one's general approach to life and summarize the tendencies of individuals (Denollet, 1993). The personality dimension of neuroticism reflects the tendency to experience emotional distress and the inability to cope effectively with stress. Highly neurotic people are extremely tense, anxious, insecure, suspecting, jealous, emotionally unstable, hostile and vulnerable (Maddi, 1980). "Although emotional distress is associated with invalid health complaints such as chest pain in the absence of coronary heart disease (CHD)(Costa and McCrae, 1987), evidence suggests that emotional distress is associated with actual CHD as well." (Friedman, 1990)(Denollet, 1993).
How is neuroticism assessed?
There is no standard assessment of neuroticism. Previously used measures of neuroticism include the total Cornell Medical Index ( CMI) Psychiatric score (Brodman, et al., 1960), the Guilford Zimmerman Temperament Survey (GZTS) Emotional Stability (Guilford et al., 1976), GZTS Emotional Health (Guilford et al., 1976), the NEO Personality Inventory (NEO-PI; Costa & McCrae, 1985), the Minnesota Multiphasic Personality Inventory (MMPI) Neuroticism Component Scale (Costa et al., 1985), the Eysenck Personality Questionnaire (EPQ; Eysenck & Eysenck, 1975), and the Eysenck Personality Inventory (EPI; Eysenck & Eysenck, 1964). Of these, the EPI, EPQ, and the MMPI Neuroticism Component Scale have become the most commonly used measures in recent years for investigating the relationship between neuroticism and cardiovascular disease.
Is Neuroticism a Psychosocial Risk Factor for CHD?
There is little evidence suggesting that neuroticism is predictive of CHD. There have been studies that have shown neuroticism and its component traits to be positively associated with occurrence of CHD, however the interpretation of these results has been complicated by several problems (Jenkins, 1971; Jenkins, 1976; Friedman, 1987). "First, neuroticism is positively associated with occurrence of a condition clinically similar to angina pectoris but not due to atherosclerotic coronary artery disease(Costa, 1987). This produces errors of classification which, because they are correlated with neuroticism, bias results toward a positive association. Second, neuroticism is positively correlated with worry about health. Persons who score high on neuroticism are more likely than others to visit physicians and, therefore, to have asymptomatic diseases discovered. This could also bias results toward a positive association because a large proportion of nonfatal myocardial infarctions are asymptomatic." (Almada et al., 1991)
Most importantly, studies finding positive associations between neuroticism and coronary heart disease endpoints have been cross-sectional. Neuroticism has not been shown to prospectively predict CHD outcomes such as myocardial infarction(MI) and CHD mortality (Costa, 1987). Four large-scale prospective studies that examined the association between neuroticism and subsequent myocardial infarction all yielded null findings(Ostfeld et al., 1964; Keehn et al., 1974; Goldbourt et al., 1975;Hallstrom et al., 1975). Because the temporal association of the variables in cross-sectional studies remain ambiguous, many prominent coronary-prone researchers (Stone and Costa, 1990; Matthews, 1988) believe that only prospective studies should be used to garner evidence about the causal role of personality in disease etiology (Costa, 1989). Although neuroticism has not been shown to predict CHD outcomes such as MI and CHD mortality, more research is needed before neuroticism should be ruled out as playing a causal role in CHD development. Validity of these studies are still quite questionable, because the best assessments currently available for neuroticism were not used in these studies, increasing the chance of interference due to confounders.
Although there is a lack of evidence suggesting that neuroticism plays a causal role in the development of heart disease, there is evidence that neuroticism is somehow associated to coronary heart disease. In a 1991 study by Cramer, neuroticism assessed using the EPI was found to be more positively correlated to self-reported coronary heart disease than Type A Behavior Pattern (TABP), a much more established psychosocial risk factor for CHD. Similar work by Lichtenstein et al., 1989 provides further support for the positive association of neuroticism with self-reported CHD. Neuroticism assessed using the EPI again was correlated with greater relative risk for CHD. Men under the age of 65 years had a relative risk for CHD of 2.56 (1.47-4.45, 95% confidence interval), while women under the age of 65 years had a relative risk of 2.73 (1.41-5.28, 95% confidence interval). Winstow et al., 1989 summarizes much of the research which has shown relationships between cardiovascular disease and neuroticism. According to Winstow et al., ten out of twelve studies found a positive relationship between neuroticism and various cardiovascular disease endpoints, such as MI and angina. This leads them to the conclusion that "in general there appears to be strong research support for a positive relationship between neuroticism and cardiovascular disease." Winstow et al., 1989 also contained the results of their own study which found that neuroticism, assessed using the EPQ, was positively associated with stress and cardiovascular symptoms. Once again, due to the temporal ambiguity of these studies from their cross-sectional nature, it is impossible to determine which one, if any, of these factors play a causal role. However, these findings supporting that stress, neuroticism, and cardiovascular symptoms may be tied together in ways that are not yet understood do show that more research is needed concerning the interaction of these factors.
Despite these findings of a positive association between neuroticism and various CHD endpoints, null findings and questions of validity over many of the studies create doubt over whether any important relationship between neuroticism and CHD exists at all. Although neuroticism has been very consistently associated with chest pain complaints and frequently associated
with subsequent diagnoses of angina pectoris, neuroticism has consistently been found not to be positively associated with stricter, more objective CHD endpoints (Stone and Costa, 1990). For example, two angiographic studies found no relationship between neuroticism and the extent of coronary artery disease (CAD)(Blumenthal et al., 1979; Zyzanski et al., 1976). Other angiographic studies actually found an inverse relationship between neuroticism and extent of CAD (Elias et al., 1982; Bass & Wade, 1984). Furthermore, these results were confirmed in studies that use other objective criteria for CHD other than angiography, such as history of MI and electrocardiogram (ECG) evidence of coronary ischemia (Costa et al., 1982). The use of strict, objective endpoints is particularly important in studies examining the relationship between neuroticism and cardiovascular disease, because of the previously discussed biases toward a positive association of neuroticism with more subjective CHD endpoints, such as self-reported cardiovascular health problems and angina pectoris diagnoses. Until neuroticism is shown to be consistently positively associated with strict, objective CHD endpoints, the neuroticism-CHD association will remain highly controversial.
Associations between Neuroticism and High Blood Pressure
Studies have also examined whether neuroticism is associated with high blood pressure. As with the neuroticism-CHD association, results have been conflicting. Three studies observed higher neuroticism scores among hypertensives (persons in clinical care) in comparison to healthy normotensives (Robinson, 1962; Sainsbury, 1964; Kidson, 1973). However, in other studies in which a nonclinical study population was used, no significant differences in neuroticism were found between hypertensive and normotensive groups in seven studies (Cochrane, 1969; Cochrane, 1973; Kidson, 1973; Schnalling and Svensson, 1984; Santonastoso et al., 1984; Almada et al., 1991; Kohler et al., 1993). Only one nonclinical study found hypertensives to have higher neuroticism scores than normotensives (Cuelho et al., 1989), while another study even found an inverse relationship, lower neuroticism scores in hypertensives as opposed to normotensives (Davies, 1970). The evidence as a whole does not support an association between neuroticism and high blood pressure. Positive findings of such an association were primarily seen in the clinical population group studies (Robinson, 1962; Sainsbury, 1964; Kidson, 1973), but have been questioned in their validity. Hypertensives in early stages often goes unnoticed for many years. The highly neurotic hypertensives are more likely to seek medical attention. Therefore, by selecting hypertensives in clinical settings, high neuroticism scores may also have been selected for.
It should be noted that in the majority of these studies, heterogeneous study populations were used in which possible confounders such as gender, age, professional status, food intake, and physical exercise were not controlled for. However, the most recent study (Kohler et al., 1993) used a large sample of 624 subjects, as homogenous as possible in the aforementioned variables, and still found no association between blood pressure and neuroticism.
Determinants of Neuroticism
There has been remarkably little research on the determinants of neuroticism, particularly social class and job stress. 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. Similarly, an adult's experience, which might include stressful, low control jobs, may shape their personality development (Kohn and Schooler, 1982). 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.
Due to a lack of positive findings in prospective studies, there is no scientific evidence that neuroticism plays a causal role in coronary heart disease or hypertension. Very few large-scale, rigorous prospective studies have been done however, and those that have often have not used standard assessments of neuroticism. Future, more carefully designed prospective studies may uncover evidence of such a causal role for neuroticism, but there is little scientific evidence to suggest such future findings will be made. Cross-sectional positive associations observed between neuroticism and various CHD endpoints or hypertension have been inconsistent and controversial. Studies that have found positive associations of neuroticism with various CHD endpoints have been flawed, because biases toward a positive association had not been avoided through the use of strict, objective CHD endpoints. Additionally, many of the studies that found support for a neuroticism-CHD relationship cited by Winslow et al., 1989 did not use strict measures of neuroticism. When more reliable, objective CHD endpoints such as angiography have been used, no evidence for a positive association between neuroticism and cardiovascular disease has been observed. Until positive correlation between valid assessments of neuroticism with strict, objective CHD endpoints are observed, there will not be strong research support for such an association. Lastly, studies that have found positive correlation between neuroticism scores and high blood pressure have also been questioned, because this relationship has only been observed in clinical populations of hypertensives where biases toward a positive association exist. Numerous studies in nonclinical settings, more reliable due to the lack of selection bias, have produced consistent null findings. Therefore, there appears to be no strong evidence for an important association between neuroticism and high blood pressure, and significant evidence against such a relationship. Lastly, very little is known about the determinants of neuroticism. 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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