Maternal overprotection score of the Parental Bonding Instrument predicts the outcome of cognitive behavior therapy by trainees for depression

Authors


Correspondence: Motoshi Asano, MD, Department of Psychiatry, Social Insurance Chukyo Hospital, 1-1-10, Sanjoh, Minami-ku, Nagoya, Aichi 457-8510, Japan. Email: mtcasano@fujita-hu.ac.jp

Abstract

Aims

The purpose of this study was to predict the outcome of cognitive behavior therapy (CBT) by trainees for major depressive disorder (MDD) based on the Parental Bonding Instrument (PBI). The hypothesis was that the higher level of care and/or lower level of overprotection score would predict a favorable outcome of CBT by trainees.

Methods

The subjects were all outpatients with MDD treated with CBT as a training case. All the subjects were asked to fill out the Japanese version of the PBI before commencing the course of psychotherapy. The difference between the first and the last Beck Depression Inventory (BDI) score was used to represent the improvement of the intensity of depression by CBT. In order to predict improvement (the difference of the BDI scores) as the objective variable, multiple regression analysis was performed using maternal overprotection score and baseline BDI score as the explanatory variables.

Results

The multiple regression model was significant (P = 0.0026) and partial regression coefficient for the maternal overprotection score and the baseline BDI was −0.73 (P = 0.0046) and 0.88 (P = 0.0092), respectively. Therefore, when a patient's maternal overprotection score of the PBI was lower, a better outcome of CBT was expected.

Conclusion

The hypothesis was partially supported. This result would be useful in determining indications for CBT by trainees for patients with MDD.

MANY OUTCOME STUDIES, including meta-analyses, have been reported regarding the efficacy of cognitive behavior therapy (CBT) for major depressive disorder (MDD).[1-3] As a result, CBT is now considered to be one of the first-line psychotherapies for MDD in leading guidelines[4-7] and there is increasing need for training in CBT among the health-care professions.

CBT requires a particular training process, and it should include clinical practice under supervision.[8] In this situation, a trainee cannot always fulfill the patients' expectation of quicker recovery from the depressive symptoms because he or she has not obtained standard skill in CBT as yet. Therefore, it would be useful to identify the group of patients with MDD who would respond well to therapy performed by trainees.

Ainsworth et al. classified various kinds of attachment styles between parents and children based on the attachment theory by Bowlby.[9-11] Parker et al. then developed the Parental Bonding Instrument (PBI) on the basis of these studies in order to measure the perceived parenting style by the children.[12] The PBI consists of four subscales: paternal care (PC), paternal overprotection (PO), maternal care (MC), and maternal overprotection (MO). There have been several studies regarding the relationship between the PBI and vulnerability to MDD, general anxiety disorder, and panic disorder.[13-18] The outcome of pharmacotherapy for MDD has also been studied in relation to the PBI. For instance, Sakado et al. reported that low levels of PC might be a predictor of a poor response to pharmacotherapy.[19] Geerts et al. reported that low MC and high PO predicted a poor response to treatment with antidepressant.[20] Although Bowlby originally suggested utilizing attachment theory to perform psychotherapy effectively,[10] only a few studies have been done on the relationship between the PBI and outcome of CBT. Chambers et al. noted lower levels of PC and higher levels of PO were reported by patients still having a clinical anxiety diagnosis 3–14 years after treatment compared to patients without diagnosis.[21] Ryum et al. reported that higher levels of PC were related to a better outcome in individual CBT for patients with obsessive compulsive disorder.[22] No study has been done, however, on the relationship between the PBI and the outcome of individual CBT for MDD as far as we know.

The aim of the present study was therefore to predict the outcome of CBT by trainees for MDD based on the PBI. We hypothesized that a higher care and/or lower overprotection score would predict a favorable outcome of CBT by trainees.

Methods

The subjects for this study were all the outpatients with MDD who had received once-a-week CBT by trainee psychologists at the Fujita Health University Hospital from October 2002 to September 2009. The diagnosis of MDD was made by experienced psychiatrists using the DSM-IV-TR. All the subjects were asked to fill out the Japanese version of the PBI[23] before commencing the course of psychotherapy. The original version of the Beck Depression Inventory (BDI), a self-rating scale for depression developed by Beck et al.,[24] was used at each psychotherapy session in order to evaluate the intensity of depression. The subjects with a BDI score <10 at the first session were excluded from this study. The BDI scores at the first and the last session were used to represent the intensity of depression at the beginning and at the end of psychotherapy, respectively. The first score was used as the baseline BDI and the difference between the first and the last score as improvement of the intensity of depression by the CBT.

The CBT was performed based on Beck's text.[8] The session was for 50 min and held 14 times in all. The first eight sessions were weekly, followed by four fortnightly and two monthly sessions. Some discretion was allowed, however, regarding the number and frequency of the sessions based on clinical judgment. Each session was reported and discussed regularly in the weekly supervision group for 50 min. All the therapists were clinical psychologists with a masters degree and clinical experience of <4 years. They were all female and aged in their 20s and 30s.

Of the 25 subjects who received CBT during that period, three were excluded because their BDI scores at the first session were 1, 3, and 6. Of the 22 potential subjects, two dropped out of treatment prematurely. Because they had had two and five therapy sessions, respectively, they were excluded from analysis. The 20 subjects eligible for analysis included six men and 14 women with a mean age of 37.1 ± 11.5 years (range, 22–65 years). The mean number of psychotherapy sessions was 14.6 ± 2.6 (range, 10–20). The mean BDI score at the first session (baseline BDI) was 20.9 ± 8.6 (range, 10–38), and the mean score at the last one was 14.2 ± 11.7 (range, 1–39). Mean improvement was therefore 6.7 ± 14.7 (range, −25 to 32). The means of the four subscales of the PBI (PC, PO, MC, and MO) were 17.9 ± 10.0 (range, 3–33), 15.8 ± 7.0 (range, 4–27), 25.8 ± 8.6 (range, 9–36), and 15.1 ± 7.6 (range, 1–30), respectively.

Pharmacotherapy, prescribed by psychiatrists, was given concurrently in 16 subjects. All the pharmacotherapy had lasted >5 months before commencing the psychotherapy. Change of the prescribed drug during psychotherapy was requested to be avoided in order to minimize the influence of the pharmacotherapy, but dosage was decreased in two subjects during psychotherapy.

This study was described to all the subjects and written informed consent was obtained from each of them. This study was approved by the Ethics Committee at the Fujita Health University School of Medicine.

Statistical analysis

Each of the PBI subscales and baseline BDI was compared with the improvement (difference of the BDI scores) by correlation analysis in order to calculate Pearson correlation coefficients. Shapiro-Wilk test was also performed in order to check the normality. Given that we predicted that the baseline BDI would influence the improvement, multiple regression analysis was performed in order to investigate whether some subscales of the PBI could predict improvement, even allowing for the influence of baseline BDI. All statistical analysis was performed with JMP 7 (SAS Institute Japan, Tokyo, Japan). P < 0.05 was considered to indicate statistical significance.

Results

Five scatter diagrams comparing baseline BDI, PC, PO, MC, and MO, with improvement were plotted. Correlation analysis was then used to calculate Pearson correlation coefficients. Regarding PO, one female subject was excluded because the scores could not be calculated, due to some blanks on the PBI questionnaire.

No significant correlation was observed on the diagrams between each of PC, PO, and MC, and improvement (PC, r = 0.075; PO, r = −0.25; MC, r = 0.32). Between MO score and improvement, a negative correlation was observed and was statistically significant (r = −0.50; P = 0.023; Fig. 1a). There was also a correlation between baseline BDI and improvement (r = 0.61; P = 0.0045; Fig. 1b). According to Shapiro–Wilk test, MO score (P = 0.47), improvement (P = 0.54), and baseline BDI (P = 0.13) were considered to be normally distributed. In order to predict improvement as the objective variable, multiple regression analysis was performed using MO score and baseline BDI as the explanatory variables. The multiple regression model was significant (P = 0.0026) and partial regression coefficients for MO score and baseline BDI were −0.73 (P = 0.0046) and 0.88 (P = 0.0092), respectively. The coefficient of determination adjusted for the degrees of freedom (R*2) was 0.45. No significant correlation was observed on the diagram between MO score and baseline BDI (r = −0.24; Fig. 1c). Therefore, a negative correlation was considered to exist between improvement and MO score, and a positive correlation between improvement and baseline BDI. In conclusion, the hypothesis was partially supported.

Figure 1.

(a) Maternal overprotection (MO) score and (b) baseline Beck Depression Inventory (BDI) score (BDI score at the first session) vs improvement (difference in first-session and final-session BDI scores). (c) MO score vs baseline BDI.

Discussion

When an assessor selects a suitable patient for CBT performed by trainees, two steps should be included in the process. First, he or she should assess the suitability of the patient for CBT itself. Second, he or she should consider the suitability of the patient for psychotherapy by trainees. Regarding suitability for psychotherapy, Peebles-Kleiger, based on her rich experience as a psychotherapist, claimed that an assessor should conduct therapy-specific formulation and a trial intervention based on it in order to determine the indications for psychotherapy.[25] This process, however, is not sufficient, to select a suitable patient for CBT by trainee. According to the present results, if a patient's MO score is lower, he or she would be a good candidate for a training case because a good outcome would be expected for CBT performed by trainees.

We will now discuss why a favorable outcome was obtained in this study with a patient whose MO score was lower. According to Beck, the CBT requires a sound therapeutic alliance.[8] Leddy et al. noted that a significant relationship had been found between the quality of the therapeutic relationship and treatment outcome.[26] Therefore, a better therapeutic relationship may have resulted in a therapeutic dyad with a better CBT outcome. According to Parker et al., the overprotection scores (PO and MO) reflect a psychological control over the child by the parents.[12] Therefore, a lower MO score represents less controlling characteristics of a maternal parenting style in childhood. In turn, less controlling characteristics of a maternal parenting style in childhood may have generated a better relationship with the therapist, which may have produced a better treatment outcome in the present study. In addition, this better relationship itself between the patient and the therapist must have been easier to manage even for the trainees, which may have also influenced the better outcome. This, however, is a hypothesis at present, and needs further study.

Limitations

There were some limitations in this study. The first point is that the number of subjects was limited. Therefore, there is a possibility of false negative, especially regarding the correlation between MC and improvement (r = 0.32).

The second point is that only the BDI, a subjective self-rating scale, was used to represent the intensity of depression. Some studies have already reported on the quick recovery of BDI score followed by improvement of the Hamilton Depression Scale (HAM-D) in CBT.[3, 27] A further study with an objective rating scale such as the HAM-D would be expected.

The third point is that a follow-up study was not performed after CBT. Therefore, there remains the possibility that the present improvement group is not exactly the same as a true recovery group without recurrence for a certain period. According to previous studies, the recurrence rate in 1–2 years of the CBT-treated subject group with depression was significantly lower than that of the group treated with pharmacotherapy.[28-30] Therefore, there is an expectation that the recurrence rate of the present subject group would be low. Still, a further study with some follow up is necessary.

The fourth point is that all the therapists were female. In this study, only MO score was correlated with outcome. There remains, however, the possibility that this may have been because all the therapists had the same sex as the mother. Therefore, a further study with both male and female therapists is necessary.

Acknowledgment

The authors declare that they have no conflict of interest with regard to this study.

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