The impact of antidepressants on seizure frequency and depressive and anxiety disorders of patients with epilepsy: Is it worth investigating?

PURPOSE: Depression and anxiety disorders in patients with epilepsy (PWE) remain under-recognized and under-treated, despite being the most common psychiatric co-morbidities. Selective serotonin re-uptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) are considered first-line treatment for primary depression and anxiety disorders. We performed this study to investigate if SSRIs and SNRIs could affect the seizure frequency of PWE and to assess whether such effect is independent of the response of the mood and anxiety disorders to these drugs.

METHODS: This was a retrospective study of 100 consecutive PWE who were started on an SSRI or SNRI for the treatment of a depressive and/or anxiety disorder. Every patient underwent a psychiatric evaluation by one of the investigators using a semi-structured interview who also managed the pharmacologic treatment in all the patients. Patients were excluded if they had a diagnosis of psychogenic non-epileptic seizures or if they had undergone epilepsy surgery or the implant of the vagal nerve stimulator six months before and after the start of the antidepressant therapy. The final analysis was conducted in 84 patients. For each type of seizure, an average and maximal monthly seizure frequency during the six months preceding and following the start of psychotropic drugs was extracted from the medical records. We identified the number of patients whose seizure frequency during treatment with antidepressants: (i) shifted from a <1/month to a ≥1 seizure/month and vice-versa, (ii) increased beyond maximal/monthly baseline frequency, and (iii) patients who developed de-novo generalized tonic-clonic (GTC) seizures.

RESULTS: None of the patients with a baseline seizure frequency <1seizure/month went on to have ≥1seizure/month after initiating treatment with antidepressants, had an increase in frequency beyond baseline maximal counts or developed de-novo-GTC seizures. Furthermore, there was no seizure recurrence among patients that had been seizure-free. Among the patients with a baseline seizure frequency ≥1/month, 27.5% had a reduction in seizure frequency to <1/month, which suggested a positive effect of SSRI/SNRI on seizure frequency (p=0.001, McNemar test). Among the patients with a baseline seizure frequency ≥1seizure/month, 48% exhibited a >50% reduction in seizure frequency after the start of treatment with SSRIs or SNRIs. A therapeutic response to SSRIs and SNRIs was found in 73% of patients. The change in seizure frequency was independent of the improvement in psychiatric symptomatology.

CONCLUSION: In this retrospective observational study, SSRIs or SNRIs did not appear to worsen seizure frequency. Also, in patients with frequent seizures, SSRIs and SNRIs may be associated with a possible decrease in seizure frequency. Furthermore, these drugs appear to yield good therapeutic response of psychiatric symptoms independently of seizure frequency. It is pivotal to replicate these data in prospective, double-blind, placebo-controlled trials.