About one patient out of two of the cohort reports depressive symptoms on waiting-list for kidney or liver transplantation. These symptoms were mainly of mild intensity, ant to a lesser extent, of moderate intensity. Although lower from those reported in general population, this result is coherent with those of the literature about report of depressive symptoms on waiting list for kidney [4
] or liver [21
] transplantation. In a context of knowledge pertaining to organ scarcity and waiting list demand, social desirability might lead transplant candidates to under-report the depressive symptoms they are experiencing in order to present themselves as better candidates for transplantation [26
]. The specificity of our results regarding report of depressive symptoms as compared to anxiety symptoms suggests that anxiety, but not depressive symptoms may be acceptable from a patient and society point of view in the context of waiting for a solid organ transplantation.
This study shows that report of depressive symptoms on waiting list predicted a 3 to 4-fold decreased risk of graft failure and mortality 18-months post-transplantation. This risk factor is independent from other risk factors such as age, gender, main primary diagnosis and length since this diagnosis. Of note, the risk of death is 3 to 4 times lower for patients who report depressive symptoms on waiting list, suggesting the clinical relevance of this association. Furthermore, data are consistent for liver and kidney transplantations despite differences between these two subgroups for socio-demographic and medical factors. Moreover, using a Short-BDI cut-off score of 7, corresponding to the higher quartile, the association between depressive symptoms and 18-month transplantation outcome showed similar odds ratios and remained almost significant despite small sample sizes. Thus, this result suggests a more general association.
This study is the first prospective cohort study in the field of liver and kidney transplantation showing an association between report of depressive symptoms on waiting list and post-transplantation outcome, since the three previous prospective studies [4
] in this field failed to show significant associations.
The four other prospective studies in the field of solid organ transplantation showed divergent results. One study [12
] in heart transplantation was non-conclusive. Another one [11
] in heart transplantation also based on self-report of depression showed contradictory results as compared to ours. However, it was conducted in a small subgroup of 57 patients with a specific cardiopathy. And the third one [13
] in lung transplantation showed results similar to ours, i.e. a better one-year post-transplantation outcome for patients who had a psychiatric history of depression before transplantation. Recently, our study [9
] showed that depressive symptoms 3 months post-liver transplantation and an increase in depressive symptoms between the waiting list and post-liver transplantation periods are associated with an increased risk of long-term mortality. The results of the present study, which show that report of depressive symptoms on waiting-list predicted a 3 to 4-fold decreased risk of graft failure and mortality 18-months post-transplantation, are somewhat different, but compatible with the previous ones. Indeed, the depression score increase between pre and post-transplantation is favored by low pre-transplantation scores. Moreover, the impact of social desirability could explain this difference: whereas social desirability is high in waiting-list, explaining low depression scores and the present association, social desirability is not relevant anymore in the post-transplantation period.
The association of depression with medical outcome has been studied in other fields than transplantation, especially cardio-vascular diseases. Even if almost half of the 57 studies reviewed by Wulsin et al (1999) [27
] failed to show any association between depressive symptoms and mortality, several published studies showed that major depression is associated with poorer outcome of medical disorders. Our results are at odds with this literature, which however is controversial, since it failed to show that treating major depression can improve outcome of medical disorders, especially cardio-vascular diseases [28
]. Three major points may explain this discrepancy. First, a publication bias may exist, penalising results similar to ours. Secondly, we focused on report of depressive symptoms and not on major depressive episodes as evaluated by clinicians with psychiatric interviews, which are assessed in a large number of published studies. Last but not least, in most studies showing an association between depression and poorer outcome, depressive symptoms were assessed during or just after an acute medical episode [29
]. In contrast, our study and the Woodman transplantation study [13
] assessed depressive symptoms very early in the process of transplantation, i.e. at the beginning of the waiting list period, in the specific context of transplantation candidacy involving social desirability. Yet those other studies are of heart attack, which are indeed acute episodes. Emotional response in the case of those waiting for transplants is a very different case, where there is not an acute episode but a long trajectory of increasingly severe illness and the prospect of death without a transplant.
There is scope for generalising the results of this study on the basis of its main strengths. First, we were able to trace, 18 months post-transplantation, all transplanted subjects from a fairly large cohort of 339 patients who were not medically selected for health status at the time of initial assessment. In addition, many of our results are in line with the literature, not only in term of report of depressive symptoms [21
], but also in terms of post-transplantation patient and graft survival [2
], causes of death [2
] and predictive factors of transplantation outcome [3
]. Moreover, the major strength of this study is that the assessment of depressive symptoms took place not a few days before transplantation, but 6 months earlier on average. This is specific to this study as compared to other available studies in the field of transplantation [4
Nevertheless, the present study has some limitations. We failed to show a relationship between the severity of depressive symptoms reported on waiting list and transplantation outcome. Any correlation would have argued for a causal relationship between these two variables. Importantly, the results of the present study do not address the risks associated with clinical depression but focus on the risk associated with self-report of depressive symptoms. Furthermore, our sample, recruited in 3 transplantation centers, may not be representative of all patients on waiting list for liver or kidney transplantation. And it cannot be ruled out that they may be explained by residual confounding variables, such as non-measured medical characteristics for example.
The mechanisms by which our main result could be explained require further studies. An hypothesis could be that recipients experiencing depressive symptoms on waiting list may be better able to identify and face later psychological difficulties, and thus be better prepared to cope with the significant stressors that occur post-transplantation [13
]. Another relevant hypothesis could be that report of lack of depressive symptoms on waiting list may be associated with report of medication non-adherence on waiting list, which has been shown to be associated with a poorer prognosis of transplantation [8
]. The role of denial might also be relevant: those who do not acknowledge depression might also be more likely to deny physical symptoms and therefore not seek help when needed or adhere to medications.