Comparative analysis and predictors of biopsychosocial functioning in various health conditions: multiple sclerosis and organ transplantation

Description

In the present Ph.D. dissertation, four empirical and pioneering works have been carried out addressing the biopsychosocial functioning of patients diagnosed with multiple sclerosis (MS) and of transplant recipients (hepatic and renal). The level of analysis of this group of pieces of research will range from a general level (all quality-of-life dimensions) in the first two papers, to specific domains of the biopsychosocial functioning (difficulties in affective processing and pain) in the third and fourth studies. Particularly, the first two works aimed to compare the quality of life of patients diagnosed with MS and of transplant recipients (hepatic and renal) in order to determine the relative impact that these medical conditions have on the biopsychosocial functioning of the affected people. The SF-36 Health Survey was administered to the following participant samples: a) with respect to the first work, 31 patients with MS and 31 liver transplant recipients, both groups matched for gender; b) regarding the second study, 30 patients with MS and 30 renal transplant recipients, both groups matched for gender and homogenized according to age and working status. Analysis of Covariance was conducted in both studies, controlling for time since diagnosis of multiple sclerosis/time since transplantation surgery until assessment (first work), and controlling for age (in the second study) as covariates. The comparative framework underlying both works is very suitable from a clinical point of view, as both populations share immunotherapy as a pharmacologic first-line treatment, thereby being exposed to similar stressors. Likewise, these two studies presented complementary study designs, cross-sectional (the first one) and longitudinal (the second one), so that the trajectory of the differences between groups could even be determined at six months from baseline. Finally, all these results were analyzed in terms of clinical significance, using two representative samples of the general Spanish population according to the specific age interval of the participant sample involved in each study. In all domains in which statistically significant differences between both clinical conditions were found, neurological patients showed worse quality-of-life levels. These differences belonged to the physical domain when the comparison with liver transplant recipients was carried out, whereas the differences were broader, both in physical and psychosocial facets, when the contrast involved renal transplant recipients. Moreover, while patients diagnosed with multiple sclerosis showed a clinically relevant deterioration in all dimensions of quality of life in both works and measurement points, transplant recipients, and especially liver transplant recipients, also showed clinically significant impairment in several domains of the biopsychosocial functioning. Therefore, it becomes clear that both these neurological patients and transplant recipients are medical populations that require special health care. The third work included in this Ph.D. dissertation was also pioneering from a scientific standpoint, by being the first work that studied the factor structure of the Toronto Alexithymia Scale (TAS-20) in patients diagnosed with multiple sclerosis, as well as the first work that addressed alexithymia in these neurological patients in Spain. Furthermore, in this study, an improved version of the Spanish adaptation of this instrument was proposed (named the TAS-20-S), with respect to those ones already available in our language. This work, which involved 221 patients, supported the traditional three-factor structure of the TAS-20 using confirmatory factor analysis, and showed appropriate reliability levels for the total scale and for each of its subscales. Therefore, these findings justify conducting future empirical research in order to assess the differential predictive value of each of the dimensions of alexithymia as measured by the TAS-20. In line with this, the fourth study aimed to determine the relative importance of the various subscales of the TAS-20-S with respect to other variables of an affective (anxious-depressive symptomatology measured by the Mental health subscale of the SF-36 Health Survey) and sociodemographic nature (age, gender and educational level), to predict various parameters of pain (intensity and functional interference using the Brief Pain Inventory, and the Bodily pain subscale of the SF-36 Health Survey) in patients with MS. Using a longitudinal design (baseline -211 patients-, at 6 months -200 patients- and at 18 months -201 patients), a new statistical method based on relative weights was used to perform a more realistic analysis of the contribution of each predictor, taking into account the actual correlation between variables and the measurement error of each predictor. All predictors belonged to the baseline of the study. Anxious-depressive symptomatology significantly predicted the various parameters of pain in all models, except for one. In turn, the subscale of the TAS-20-S, Difficulty Identifying Feelings, statistically predicted the SF-36 Bodily pain subscale and functional interference due to pain, both parameters belonging to the third measurement point of the study -18 months after baseline. Interestingly, in the latter two models where Difficulty Identifying Feelings was a significant predictor, no statistically significant differences were found between this alexithymic dimension and anxious-depressive symptomatology in predicting the above-mentioned facets of pain (SF-36 Bodily pain subscale and functional interference due to pain). These results indicate that psychological interventions to treat pain in patients with MS should address negative affect and alexithymic difficulty identifying feelings as well as differentiating between feelings and the somatic sensations associated with affective arousal.

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