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Aim: Adult patients with type 2 diabetes were classified using the Temperament and Character Inventory (TCI). This classification was used to propose effective therapeutic approaches based on subtypes of psychological characteristics.
Methods: The TCI and various psychological tests were administered to 89 patients (54 men and 35 women). Cluster analysis was performed using three temperament factors of the TCI as variables for subclassification: novelty seeking (NS), harm avoidance (HA) and reward dependence (RD).
Results: The patients were divided into two clusters based on the TCI results. Cluster 1 had a low NS/high HA/low RD pattern, which indicated resistance to change and lack of cooperativeness, and results of other tests indicated that patients in cluster 1 were obsessional and had weak intention and personality disorder symptoms. In contrast, cluster 2 had a high NS/low HA/high RD pattern, indicating a socially active person who easily becomes dependent on others, and results of other tests indicated that these patients were histrionic and less anxious. In cluster 1 there was a significant negative correlation between hemoglobin A1c (HbA1c) and SD-1 (TCI self-directedness) ‘responsibility’ and a significant positive correlation between HbA1c and State anxiety of State–Trait Anxiety Inventory. In cluster 2 there was a significant positive correlation between HbA1c and HA-2 ‘fear of uncertainty’.
Conclusions: Patients with type 2 diabetes were classified using the TCI into two subgroups. These two groups differed in psychological characteristics and had a different pattern in correlation with glycemic control.
THE THERAPEUTIC TARGET of diabetes treatment is maintenance of good glycemic control and prevention of complications. This requires patient self-management of activities such as exercise and eating habits. Because therapeutic effects vary depending on the degree of self-management, techniques to promote these skills are necessary1 and psychotherapy is reported to be effective.2 For effective support, an understanding of the psychological characteristics of the patient is necessary.
In previous studies, depression has been found in approximately 30% of all diabetic patients,3 40% of diabetic patients under treatment had anxiety symptoms,4 and diabetes doubled the risk of depression.5 Factors associated with poor glycemic control include depression,2,6 anxiety,7 alexithymic tendency,8 extreme personality features,9 and stress load,10 whereas problem-solving ability11 and diabetes locus of control12 are factors associated with good glycemic control. An empowerment approach with psychological support to increase the self-worth and self-control of the patient has been shown to increase the therapeutic effect.13 Therefore, psychological conditions have a major influence on glycemic control, and effective treatments have been designed based on these findings.
The current study was based on the hypothesis that there are plural personality patterns in diabetic patients. This hypothesis was established because contradictory findings regarding diabetic characteristics have been reported. One study found that fewer negative emotions and altruistic features are associated with poor glycemic control,14 whereas lack of relationship between personality and level of glycemic control has also been reported.15 We began to suspect that diabetic personality is not homogenous or stereotypical; that is, diabetic personality may be subclassifiable and this may lead to treatment approaches that correspond to particular characteristics and thus may be more effective. The study design was planned on this basis; we first divided the patients into subgroups, and then investigated differences in the relationship between glycemic control and psychological test results.
The Temperament and Character Inventory (TCI) was used for classification of the personality of patients with type 2 diabetes. The degree of glycemic control has not been investigated previously with regard to personal ‘temperament’ and ‘character’, which form the basis of personality independent from psychological conditions according to the Cloninger personality theory.16–19 This theory is based on Cloninger's original biosocial model and the TCI is reported to be effective for classification of patients based on personality differences.20–22