Which comes first, depression or WED? In this study, people with depression had WED 31% of the time - but there was no correlation as to which came first.
Below is only the discussion portion - it's a long article:
This study found that RLS was frequent in the persons suffering from depressive illness compared to the general population. Earlier studies have found that depression is more prevalent in subjects with RLS.[10,11] Earlier studies addressing the prevalence of RLS in community sample suggested prevalence rates between 0.9% to 8.3% in Asian community and 17.7% in American community.[4,10,12] Only one study has examined the frequency of RLS in depressed subjects and reported prevalence of 27%. We have found nearly similar prevalence in this study.
RLS has female predisposition in earlier studies.[10,11] However, we did not find any difference between genders. Perhaps, sample selection might have played a role. Earlier studies have included RLS sufferers and then looked for depression while we did the opposite. Other epidemiological studies cannot be compared with this study as this study was clinic based.
Whether RLS leads to depression or depression leads to or aggravates RLS symptoms is a debatable issue. Previous studies suggested that psychiatric morbidity is frequent in subjects with RLS.[4,10,13,14] However, contradictory data are also available, at least in subjects with mild RLS. Our study suggest that onset of RLS symptoms was unrelated to onset of depressive symptoms. A large, prospective study addressing this issue is warranted to reach to any conclusion. Present evidence indicates that RLS may either precede or follow depression.
RLS patients often suffer from chronic insomnia and its clinical presentation frequently masquerades or induce depression.[3,10,17] thereby favoring the notion that RLS precedes depression. Hornyak et al. suggested that severity of RLS correlated with severity of insomnia but not with depression score. In addition, RLS subjects score high on only those items of depression rating scale which are consequent to insomnia corroborating lower HAM-D scores in the present study. Thus the present literature is inconclusive regarding the role of insomnia in the development of depression in RLS patients! Our results did not find any difference in the prevalence of insomnia (primary and combined) in either of the groups suggesting that insomnia may be an independent factor which does not affect RLS.
A number of factors during depressive illness may increase the likelihood of development of RLS. It is known that RLS symptoms are often aggravated during periods of stress and with the antidepressant therapy.[3,18] Mirtazepine has been found to induce RLS more frequently compared to other antidepressants including SSRI.[18,19] In the present study, most of the patients had longstanding illness spanning upto 10 years and were taking antidepressants off and on. Since, RLS was never screened they were not able to recall its relationship with antidepressant therapy. This could be a confounding factor in present study. Our data suggest that depression may not predispose a person to RLS as total duration of depressive illness, duration of present episode, “number of depressive episodes” and family history of psychiatric illness were not different between two groups.
Pathophysiologically dopamine is implicated both in depression and RLS. Benes et al. concluded that dopaminergic treatment of RLS improved the depressive symptoms and antidepressants should be advised when resolution of RLS does not improve the depressive symptoms. This must also be kept in mind that dopaminergic agonists possess an antidepressant property. It may be a simplistic view as treatment of RLS actually improves sleep quality and abolishes insufficient sleep syndrome. The latter can masquerade depression, hence, we need more data to assess these issues.
This study has some methodological limitations. Firstly, the sample size is small owing to robust exclusion criteria and hence, results are difficult to be generalized. Secondly, the data were retrospective and recall bias cannot be excluded in this group. Thirdly, a number of subjects were taking antidepressants at the time of presentation which could have aggravated RLS. Fourthly, owing to cross-sectional design we could not evaluate the effect of treatment of RLS on depressive symptoms or vice versa.
Nonetheless, this study is still important as it throws light on the possible comorbidity in depressive illness that can reduce the chances of remission of depression or precipitate future episodes. Large-sample prospective studies in future are required to reach to a conclusion on this issue.