Depression in epilepsy is multifactorial in nature and has been shown to be influenced by a number of factors.

Gender
In contrast to the increased prevalence of depression in females, a number of the studies have found men to be at a greater risk of depression as compared to females (Fenton 1986, Septien et al. 1993, Strauss et al. 1992).

Sinistrality
Some studies (Ashtuler et al. 1990) have observed that left-handed people with epilepsy have an increased prevalence of psychiatric morbidity, especially depression. A possible explanation advanced is that the expression of left-handedness may indicate early brain injury.

Related neurological conditions
The causative neurological condition responsible for the epilepsy such as multiple sclerosis, cerebrovascular accidents, dementia and Head injury may be associated with depression. Taylor (Taylor 1972) and Koch-Weser (Koch-Weser et al. 1988) suggested depression to be more common in patients with a structural lesion; this however, has been refuted by other investigators (Hermann 1989).

Genetic
Family history of psychiatric illness, usually depression (Robertson et al. 1987) and suicide (Hancock 1971), has been associated with an increased incidence of depression.

Structural changes in the medial temporal lobe
There is an emerging literature that links amygdala enlargement (Tebartz van Elst 1999) and hippocampal atrophy (Baxendale 2005) with depression (and other forms of psychopathology) in epilepsy. While the findings are by no means ubiquitous, they pose interesting questions about the role of these structures in the development of depression and the differentiation between its characterological and symptomatic components.

Past history
Past history of behavioural disturbance in infancy (Moller 1990), neurotic disorders (Roy 1979), deliberate self-harm (Palia, 1986) and depression (Lund 1985) have all been implicated in the development of depression.

Learning disabilities and IQ
Patients with learning disability and concomitant epilepsy have been shown to have twice the percentage of psychiatric disorders (including behaviour problems and autism) as compared with patients with epilepsy (Mignone et al. 1970). Psychiatric disorders are also more common in patients who had experienced seizures in the preceding year and have been found to be inversely proportional to IQ.

Age-at-onset and duration of epilepsy
Although most studies have found no relationship between age-at-onset or duration of epilepsy and depression, some studies have described an increased prevalence of depression in patients with late-onset epilepsy (Hermann et al. 1996).

Seizure type
A number of studies have reported depression to be more common in patients with CPS (Lambert 1999), and in individuals with MTS (Quiske et al. 2000). Controversy however, exists over the prevalence of increased psychiatric morbidity in patients with TLE, with studies for and against the same.

Stigma
Epilepsy has long been associated with satanic possession and evil. A positive relationship has been shown between perceived stigma and affective disorders (Hermann et al. 1996).

Psychosocial factors
Patients with a pessimistic, attributional style have an increased prevalence of depression (Hermann et al. 1996). Other factors such as increased, stressful life events, poor adjustment to seizures and financial stress have also been associated with increased depression.

_{Author(s) : R Seethalakshmi, Ennapadam S Krishnamoorthy , The Institute of Neurological Sciences, Voluntary Health Services, Taramani, Chennai, India.}

Summary : 1) Depression is a common and important accompaniment of epilepsy. 2) Depression in epilepsy is phenomenologically different from the usual forms of depression and it is essential that treating physicians assess for these varied forms as well. 3) Depression in epilepsy may be managed more effectively if the relationship to the ictus is better understood. 4) Other factors such as stressful life events, related or unrelated to epilepsy, may contribute to the depressive symptoms. 5) Antiepileptic drugs, particularly GABAergic agents such as vigabatrin, tiagabine, topiramate and phenobarbitone are depressogenic in nature. 6) The newer antidepressants, SSRIs such as sertraline, citalopram and paroxetine do not lower seizure threshold and can be safely used to treat depression in epileptic individuals. Fluoxetine may be avoided because of its longer half-life.

Keywords : epilepsy, depression, classification, etiology, treatment, SSRI

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