Personality characteristics in each cluster
Cloninger investigated the basic stimulus–response characteristics in traditional personality categories using a combination of three temperament factors (NS, HA and RD) and obtained the results shown in Table 4.16 Based on this analysis, patients in cluster 1 (low NS/high HA/low RD) were obsessional and those in cluster 2 (high NS/low HA/high RD) were histrionic. NS is related to triggering behavior and represents the extent to which novel stimulation is accepted, thereby serving as an index of eagerness for investigation or a preference for repetition, impulsiveness or calm and stoic behavior, and a tendency for spending or saving money. HA is related to inhibition of behavior and is associated with worrying and pessimism, thereby serving as an index of cautiousness and seeking assurance or optimism with overconfidence, a preference for shyness and quiet inactivity or active stimulation, and a need for a long or short time for adaptation. RD is related to maintenance of behavior and is associated with social friendly relations and sensitivity, thereby serving as an index of attaching greater importance to cooperation with companions or distancing oneself from others and hiding inner feelings, and sensitivity or indifference to social admiration, approval, and rejection.
Table 4. Basic stimulus-response characteristics of traditional personality categories, as defined by Cloninger16
Cluster 1 has a low NS/high HA/low RD pattern that indicates resistance to change in accustomed styles and a lack of flexibility, but tolerance of solitude and engagement in practical thinking unaffected by sentimental feelings. This pattern consists of weak objective-directed behavioral control indicated by the low SD score, low C, poor ability to describe feelings, high anxiety and depression, worry, and easily feeling fatigued. In contrast, cluster 2 consists of a high NS/low HA/high RD pattern that indicates an extrovert, social, emotional, and active personality that adapts to different environments, is easily dependent on others, and is easily affected by sentiments. Social solitude is painful, and persons of this type tend to force themselves to look for adaptation.26 They are able to behave with intention and are cooperative, and their alexithymic tendency, anxiety and depression levels are low.
Clusters and glycemic control
In cluster 1, anxiety increased and responsibility decreased as glycemic control worsened. The characteristics of the patients (low NS/high HA/low RD) suggest that they may have anxiety toward new treatment and may become resistant to it. Such patients may also have anxiety regarding a danger such as hypoglycemia, and may try to prevent it by taking excessive calories, leading to a tendency for hyperglycemia. Regarding their low responsibility, these patients are less aware of self-involvement in their own behavior and its outcomes, and may easily accuse others. Therefore, they may exhibit similar attitudes to treatment for diabetes and life management, such as diets and exercise, leading to poor glycemic control.
Cluster 1 was typed as obsessional, and the SD and C scores were low, suggesting personality disorder symptoms19 and showing weak intention and low C. Such patients are bound by order, perfectionism and unity, and flexibility, openness and efficiency are sacrificed. They demand that others obey their ways, and may strongly resist instructions that intervene in their lifestyles and demand changes in a one-sided manner, even when instructions are provided as therapy. But if these patients are convinced and accept the instructions, rather than being persuaded by a physician, they may maintain glycemic control methodically. Thus, responsibility may be the key to glycemic control in this patient class.
Cluster 2 was typed as histrionic, and glycemic control improved as fear of uncertainty decreased, suggesting the influence of secretion of stress hormones. This can lead to poor glycemic control in patients who are sensitive to uncertainty and easily feel anxiety, although these patients are included in cluster 2, in which depression and anxiety are relatively low. These patients are less likely to have a fear of new treatment and tend to respond bravely to such treatment, which may lead to good glycemic control. Cluster 2 patients are originally less anxious: the SD and C scores were high, showing intentional behavior and C, and they do not have difficulty in establishing a therapeutic relationship. But fear of uncertainty (i.e. cautiousness) may interfere with glycemic control. These correlations should be carefully considered because the study had a cross-sectional design and glycemic control may have affected the test scores.
For some cluster 1 patients the following psychological support may be necessary: drug therapy and/or cognitive therapy reducing depression and anxiety, elevation of awareness of self-responsibility and promotion of active involvement to increase self-worth, supporting autonomy to increase feelings of control,27 setting therapeutic goals with the support of medical staff rather than being given treatment by attending physicians, therapy attaching greater importance to self-directed individual styles, and narrative-based medicine, in which patients ‘spin the story’ themselves.28,29
In contrast, for cluster 2 patients, group treatment is appropriate because they are social and cooperative. The presence of other patients as models reduces the fear of uncertainty, which may lead to better glycemic control. A previous study has shown that patients treated in group consultations had better glycemic control than control subjects.30 Active introduction to groups, such as a diabetes group education class, is appropriate because a syntonic atmosphere is better than a focus on individuality. Cultivation of a sense of solidarity with the entire group, that is, heading for a common goal through teaching and encouragement of each other, may be more effective for patients in cluster 2.
Limitations of the study
There were four major limitations in the study: the relatively small sample size; lack of controls; cross-sectional research design that might have resulted in current glycemic control affecting the test scores; and the concern that diabetic patients do not typically have particularly pathological personalities, compared with personality deviations of anorexic or bulimic patients or patients with alcohol dependence. This may lead to a limitation in demonstrating a significant relationship between glycemic control and personality features in diabetic patients. These limitations need to be addressed in a future study with a greater number of patients and healthy controls with a longitudinal research design.
Patients with type 2 diabetes were classified into two subgroups using the TCI. These groups differ in psychological characteristics, which had different patterns in correlation with glycemic control. The results suggest that diabetes self-management support should be based on the psychological characteristics of subtypes of patients.