Epidemiology Of Depression And Anxiety In Epilepsy

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Depression is believed to be the most common psychiatric disorder among individuals with epilepsy (Hermann et al., 2000; Kanner, 2003) . For centuries a link between epilepsy and depression was hypothesized. A poignant example is evidenced by the Hippocratic corpus written around 400 BC. It stated "melancholics ordinarily become epileptics and epileptics melancholics ..." (Lewis, 1934). More recently, Hesdorffer et al. (2000) found that individuals with epilepsy were 3.7 times more likely to have a depressive episode prior to the first seizure. In a study in Iceland among children and adults with epilepsy, similar results were reported, revealing individuals with epilepsy were 1.7 times more likely to have a history of major depression prior to the first unprovoked seizure (Hesdorffer et al.) 2006). Depression appears to be a risk factor for the onset of seizures, and depression appears to be a significant comorbidity after the seizure disorder is diagnosed.

There continues to be some controversy regarding the exact incidence and prevalence rates of depression in epilepsy due to differing methodologies (self-report vs. psychiatric interview) and samples (population vs. hospital based). In studies utilizing Diagnostic and Statistical Manual of Mental Disorders (DSM) or International Classification of Diseases (ICD) (World Health Organisation, 1992) diagnostic criteria, rates of depressive disorders range from 6% to 64% (see Table 7.1). Swinkels et al. (2006) utilized the Composite International Diagnostic Interview (World Health Organization, 1992) to identify psychiatric disorders and found major depression in 21% of individuals with temporal lobe epilepsy (TLE) and 23.4% with extra-TLE. There were no significant differences between the TLE and extra-temporal groups in rates of depression. In a sample of adults with complex partial seizures, Wiegartz et al. (1999) reported 31.6% met criteria for a lifetime episode of major depression and 9.2% were identified with a current episode of major depression. This study utilized the Structured Clinical Interview for DSM-IV (SCID-IV) to identify episodes of depressive disorders (First et al.) 1996). Using the DSM-III-R criteria, Victoroff et al. (1994) identified a lifetime history of a depressive disorder in 64% of the sample and 30% had a lifetime history of major depression. Even among studies utilizing DSM or ICD criteria, there remains variability in prevalence rates of depression in epilepsy.

Like depression, symptoms of anxiety can be exacerbated by seizure activity (peri-ictal, ictal, postictal) and can appear separately or, in other words, interic-tally. Historically, anxiety and epilepsy have been viewed as highly interconnected. Temkin (1971) documented that even in the 1800s it was believed fright could cause epilepsy. Also similar to depression, methodological issues exist when determining the prevalence and incidence of anxiety disorders. Throughout the literature, hospital- or community-based samples are utilized, making it difficult to make generalizations across studies; uniform methods are frequently not used to assess or measure symptoms of anxiety (symptom checklist vs. interviews), and control groups are frequently omitted (Scicutella, 2001).

In light of these limitations, rates for anxiety disorders are reportedly elevated among individuals with epilepsy and range from 5% to 25% (see Table 7.2). A brief summary of three of these studies follows. Silberman et al. (1994) assessed individuals with epilepsy from a tertiary care center using the Schedule of Affective Disorders and Schizophrenia Lifetime Version (SADS-L) (Endicott and Spitzer, 1978), and 15% met criteria for an anxiety disorder and 16% reported symptoms of anxiety on self-report measures. Glosser et al. (2000) utilized the SCID to assess individuals with TLE prior to surgery and reported 18% of the total sample met criteria for an anxiety disorder in the previous 12 months. Among Dutch individuals with generalized and complex partial seizures, Swinkels et al. (2001) found 30% of the sample met criteria for a lifetime anxiety disorder and 25% meet criteria in the past 12 months. Much like depression, it appears that anxiety disorders are also elevated in epilepsy.

TABLE 7.1 Rates of lifetime depressive disorders

TABLE 7.2 Rates of lifetime anxiety disorders

Altshuler et al. (1999)

5%

Glosser et al. (2000)

18%

Manchanda et al. (1996)

11%

Ring et al. (1998)

18%

Silberman et al. (1994)

16%

Swinkels et al. (2001)

30%

Research findings in epilepsy are inconsistent regarding the prevalence rates of depression and anxiety among different seizure types (e.g., TLE vs. generalized epilepsy). Perini et al. (1996) found individuals with TLE to have higher rates of affective and personality disorders compared to individuals with juvenile myoclonic epilepsy and individuals with diabetes. In the same year, Manchanda et al. (1996) found no significant differences in rates of psychiatric disorders among individuals with localization related vs. generalized seizures. Additionally, in regards to laterality of the seizure focus, there were no significant differences in rates of psychiatric disorders. These two studies reflect the conflicting results reported in the literature and amplify the need for further research.

Depression and anxiety are significant comorbidities in epilepsy. Both psychiatric disorders negatively impact quality of life (Gilliam et al., 2003; Boylan et al., 2004, Johnson et al., 2004). If depression and anxiety are ignored or left untreated there is a greater likelihood for increased rates of suicide and suicidal ideation (Robertson, 1997 , Jones et al., 2003). This chapter will review the following topics: (1) co-occurrence of depression and anxiety and common symptomatology; (2) common pathogenic mechanisms; (3) treatment strategies shared by both disorders; and (4) future implications for clinicians and researchers.

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How To Win Your War Against Anxiety Disorders

How To Win Your War Against Anxiety Disorders

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