3.1. Participants and procedures
A cross-sectional study was used to examine the association between pain, depression and early maladaptive schema and to identify predictors of pain in chronic pain patients. The protocol of the study was approved by the "Regional bioethics committee". According to accepted statistic criteria a sample size between 100 and 200 subjects is considered adequate for studies involving parsimonious models to be estimated by structural equations (47). The sample composed of 100 patients with chronic pain. These patients were recruited from an outpatient chronic pain clinic affiliated with Lorestan University of Medical Sciences. Of the initial sample of 115 patients, 15 (13.04%) were excluded because of incomplete data. The final sample consisted of 100 patients, including 72 (72%) females with a mean age of 45.46±12.67 years and 28 (28%) males with a mean age of 40.68±13.99 years. The mean length of total education was 13.07± 2.72 years (range 9–18 years). The mean length of duration of pain in total sample was 5.67± 5.74 years. Men and women did not differ in age, duration of pain and education.
Inclusion criteria were: 1) receiving the diagnosis of chronic pain by a neurologist and spine specialist 2) age 18-70 years old 3) being able to write and read 4) willingness to participate in the study. Patients were excluded if: 1) had dementia and mental retardation 2) were unable to write and read or were not agree to be participated in study.
The procedure was as follow: First patients were visited by a neurologist and spine specialist and the diagnosis based on experimental criteria was established. Then for those who fulfilled the inclusion criteria, the aim and the process of the study along with confidentiality of the gathered information were described. If the patient agreed to continue and was orally consent to participate in the study, then they were asked to complete 4 questionnaires including socio-demographic data form, depression subscale of Hospital Anxiety and Depression Scale (HADS), third edition of Young’s Schema Questionnaire(YSQ-SF3) and McGill Pain Questionnaire (MPQ).
3.2.1. Young Schema Questionnaire—Short Form 3(YSQ-SF3) Based on the framework of schema therapy, the Young Schema Questionnaire (YSQ-SF3) was developed by Young, Klosko, and Weishaar(30). The original scale has 18 subscales grouped into 5 schema domains as follows: disconnection and rejection (schemas of emotional deprivation, abandonment, mistrust/abuse, social isolation, and defectiveness), impaired autonomy and performance (schemas of failure, dependence, vulnerability, and enmeshment/ undeveloped self), impaired limits (schemas of entitlement and insufficient self-control), other directedness (schemas of subjugation, approval-seeking, and self-sacrifice) and Over-vigilance and inhibition (schemas of emotional inhibition, unrelenting standards, negativity/pessimism, and punitiveness). The questionnaire consists of 90 self-report items that are rated on a six-point Likert-type scale (1 = entirely untrue of me, 6 = describes me perfectly). As each subscale consists of five items, the score obtained on the subscales varies between 5 and 30.
Soygüt , Karaosmanoglu , and Cakir (48)has shown good levels of validity and Reliability. The reliability and validity of the YSQ-SF extended in Iranian language has been (49). In our study the Cronbach's alpha coefficients for the YSQ-SF3 subscales range between .74 and .90.
3.2.2. Hospital Anxiety and Depression Scale (HADS)HADS is a self-report scale which was developed for detecting symptoms of anxiety and depression in non-psychiatric patients from a medical outpatient unit. It contains two seven-item subscales: one for depression and one for anxiety, with a score ranging from 0 to 21. Every item has a choice of 4 fixed response statements (weighted 0-3). A score of 8 to 10 points indicates borderline significance for either scale, but less than 8 points is insignificant. A cut-off score of 7 was used because investigations have shown that this is optimal for detecting psychiatric morbidity(50). The reliability and validity of the HADS to detect mood disorders has been recognized (51). In general the Iranian version of the HADS can be considered reliable and valid. Cronbach's alpha coefficient (to test reliability) has been found to be 0.86 for the HADS depression sub-scale and 0.78 for the HADS anxiety sub-scale (52). In the present study, the Cronbach's alpha coefficient for the HADS depression sub- scale was 0.84.
3.2.3. McGill Pain Questionnaire (MPQ) is a self-reporting measure of pain used for patients with a number of diagnoses. It assesses both quality and intensity of pain patients. The MPQ is composed of 78 words, of which respondents choose those that best describe their experience of pain. 7 words are selected from the following categories: dimension 1 to 10 (pain Sensory), three words; dimensions 11 to 15 (pain affective), dimension 16 (pain Evaluative) one word, and dimension 17 to 20 (pain miscellaneous) one word. Scores are formulated by summing values associated with each word; scores range from 0 (no pain) to 78 (severe pain). Qualitative differences in pain may be reflected in respondent’s word choice (53).
3.3 Statistical Analysis
Structural equation modelling (SME) were conducted using AMOS-18. These models permit to include variables that are correlated with, and can be used to predict other variables. Parameter estimates, including factor loadings, indirect and total associations, and path coefficients for direct, and residual error variance terms for criterion variables, were examined for statistical significance. The following criteria were used as indexes of acceptable model fit: 1. - the likelihood-ratio chi-square statistic (Χ2/df < 3); 2. - Goodness of Fit (GFI) >0.90; 3. - Adjusted Goodness of Fit Index (AGFI) >0.90; 4. - Root Mean Square Error of Approximation (RMSEA) <.05; 5. - Comparative Fit Index (CFI) >0.90(47).
Analysis process started with a model defined from theoretical approach (Figure 1). This model is adopted from the stories of chronic pain patients. The basic structure of this model is similar to the study by Saariaho et al., (41). A SEM of latent variable was developed with depressiveness as a mediator between latent variable and pain. SEM required selection of beginning and endpoints in the cyclical model and pain was designed as the endpoint for the model. As shown in Fig. 1, the latent construct General Maladaptive Schema (GMS) was specified by five schema domains: disconnection and rejection, impaired autonomy and performance, impaired limits, other-directedness, over vigilance and inhibition. Amos software path analysis was conducted to test the model which showed the direct and indirect effects of GMS on pain with the mediation of depressiveness.