Depression correlates with quality of life in people with epilepsy independent of the measures used
Introduction
Depression is the most frequently reported psychiatric comorbidity among patients with epilepsy. The lifetime prevalence rates range between 24% in community-based studies [1] and 50% in tertiary referral centers or surgery programs [2]. Reasons for such a close link are both biological and psychosocial [3]. In fact, on the one hand, epilepsy is a chronic disorder which brings about social discriminations, burden, and limitations [4]; on the other hand, neuroimaging and neurobiological studies are emphasizing the biological contribution to this association based on neuroanatomical and neurochemical principles [5]. This is further supported by epidemiological studies suggesting a bidirectional relationship between the two disorders, namely that depression does not always follow the onset of the epilepsy but it may also precede the onset of a seizure disorder [6], [7], suggesting an underlying common neurobiological background [8].
A number of studies pointed out that depression is the most important predictor of quality of life (QoL), perhaps even more than seizures themselves [9], [10], [11], [12]. In addition, depression has been shown to be associated with poor response of epilepsy to antiepileptic drugs (AEDs) [13], as well as poor outcome after epilepsy surgery [14]. So far, the effect of depression on QoL in patients with epilepsy has been demonstrated using the same QoL scale, namely Quality of Life in Epilepsy (QOLIE, either 89 or 31). Moreover, most of the studies have used the Beck Depression inventory (BDI) as a measure for depression and, only recently, the Hospital Anxiety and Depression scale (HADS). While the evidence to date shows a strong correlation between depression scores and QoL, it remains unclear whether this is a true effect or a function of potential biases associated with the specific scales used, namely QOLIE and Beck Depression inventory (BDI) or Hospital Anxiety and Depression scale (HADS).
This study aimed to examine the association between depression and QoL in patients with epilepsy using a different independently validated QoL instrument consisting of a visual analogue scale and four different validated measures of depression including a visual analogue scale-based instrument. The potentially different impact of different forms of depression, satisfying DSM-IV criteria and atypical forms or subsyndromic forms, on QoL was also examined.
Section snippets
Methods
This study included data collected as part of a service improvement project at the Outpatient Epilepsy Clinics, Atkinson Morley Neurosciences Centre, St George's Hospital in London. Over a ten-month period, as a routine, all patients with an established diagnosis of epilepsy according to ILAE criteria were given a number of questionnaires including those for mood and QoL. Patients with severe learning disabilities, gross cognitive abnormalities, or poor English language skills were excluded
Results
Our sample included 261 patients. Clinical and demographic characteristics are shown in Table 1. The EQ-VAS scores inversely correlated with all measures of depression with coefficients ranging between r = − 0.509 (p < 0.001) for BDI-II and r = − 0.420 (p < 0.001) for NDDI-E (Table 2). Adjusted linear regression scores and scatter plots are shown in Fig. 1.
Utilizing the MDI, 41 patients received a DSM-IV diagnosis of major depression (MD) while 90 had a positive screening with the NDDI-E. We, therefore,
Discussion
Our results confirm that QoL correlates with depression in patients with epilepsy irrespective of the instruments used to measure either QoL or depression including the use of visual analogue measures. This suggests that the correlation of depression with QoL is a valid effect and not a function of potential biases of the individual scales used. In fact, the EQ-VAS is a visual analogue scale and, by definition, neutral in terms of specific items that might have a strong correlation with
Disclosures
Alex J Mitchell holds the copyright on the revised Emotional Thermometers tool but has made it freely available (royalty-free) for noncommercial and clinical use. The remaining authors have no conflicts of interest. We confirm that we have read the journal's position on issues involved in ethical publication and affirm that this report is consistent with those guidelines.
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