Dercum’s disease is characterised by obesity, chronic pain and other associated symptoms. Some of the associated symptoms, previously described in case reports on Dercum’s disease [6
], include depression and symptoms associated with depression, such as asthenia, weakness, fatigue, emotional instability, mental confusion, dementia, poor sleep quality and changes in appetite. Several studies have demonstrated that there is a significant association between depression and pain [5
], as well as between depression and obesity [11
]. Patients with depression are often diagnosed with chronic pain conditions and vice versa [5
]. Some studies have demonstrated that depression predicts obesity later in life [11
], and other studies support that obese subjects develop depression to a greater extent than subjects with lower, “normal” body weights [12
]. Nonetheless, it is unclear whether there is a causal relationship between the three entities. The possible co-morbidity could be explained by Berkson’s bias
], that is, patients with an illness might seek care more often. Thus co-morbidity could be overrepresented in a group of subjects that are, as in this study, recruited from a care setting. In summary, it is difficult to separate chronic pain from depression.
The elevated MADRS scores in the Dercum patients in this study cannot be explained by obesity alone, as the distribution of the Dercum subjects’ scores was different to that of the weight-matched control patients (Figure
), and there was a statistical difference for the total score between the two groups (Table
). The lack of statistical difference for a number of the items could be explained by low power, that is, by the small number of subjects in the control group (n
40). The results suggested that the obese Dercum patients experience worse depression than obese healthy controls. As all of the Dercum patients had chronic pain whilst none of the controls had any history of chronic or present acute pain, it is unclear whether the depression is due to the Dercum’s disease per se
or due to the experience of pain. Furthermore, it is unclear whether the depression or the Dercum’s disease came first. Previous research has shown that antidepressants have an effect on pain and the quality of life in patients with chronic pain [14
] and that obese patients could benefit from the treatment of any co-existing features of depression [14
An example of an associated symptom in Dercum’s disease that can also be explained by depression is poor sleep quality. Poor sleep quality can diminish an individual’s ability to cope with pain and stress and can influence the onset and course of disease [16
]. In fact, a study on patients with chronic pain conditions demonstrated that sleeping less than 8 hours per 24 hours, especially in combination with poor sleep quality, might generate stronger reactions to pain [17
]. In addition, Affleck et al. concluded that there is a correlation between sleep quality and experienced pain intensity, as well as the ability to cope with pain, among patients with fibromyalgia [18
]. It can be speculated, therefore, that poor sleep can contribute to the onset of Dercum’s disease and the maintenance of pain. Conversely, obesity can also affect sleep quality [19
]. Obstructive sleep apnoea (OSA) and Pickwick syndrome [1
], both of which have been previously described in Dercum’s disease, can be explained by obesity, as 50% of otherwise healthy obese women with BMI >40 have OSA and more than 29% of severely obese patients have nocturnal hypoventilation [20
]. This could explain why no difference can be seen between the Dercum patients and the control subjects in this study, as all of the subjects have similar BMIs.
One advantage of the present study is that the same consultant made the diagnosis of Dercum’s disease in all of the cases and that a control group of healthy obese subjects was included. Furthermore, an instrument was used to measure depression that has been previously validated and extensively used in research studies focusing on depression and patients with chronic pain [10
]. A disadvantage is the fact that a normal weight control group was not included. However, there was an opportunity to include a control group of healthy obese subjects, which means that the hypothesis that signs of depression in Dercum’s disease could be explained by obesity alone can be excluded. Another weakness is the low number of patients included in this study, which is as a result of the rarity of the condition. Furthermore, it should be noted that the results are only valid for women as all of the subjects included were female.