Light Therapy Reduces Depressive Symptoms in Epilepsy

Deborah Brauser

March 28, 2013

The use of bright light therapy may reduce symptoms of anxiety and depression in patients with epilepsy, new research suggests.

A study of 101 adults with focal epilepsy showed that those who received high-intensity light therapy and those who received low-intensity light therapy had significantly lower scores on the Hospital Anxiety and Depression Scale (HADS) after 12 weeks of daily treatment.

Surprisingly for the investigators, there were no statistically significant differences in symptom scores between the 2 groups.

"Although we found that people who were clinically depressed responded better to the high-level than the low-level light, it was interesting to see that in the group as a whole, people who had the low-level light did just as well. We weren't expecting that," lead author Sallie Baxendale, PhD, CPsychol, from the Department of Neuropsychology at the National Hospital for Neurology and Neurosurgery in London, United Kingdom, told Medscape Medical News.

"It could be that the group effect we observed was not directly related to the light per se but due to the imposition of a regular morning routine. More work is needed to work out whether this explains the results," added Dr. Baxendale.

Still, she recommends that clinicians consider trying a light box to treat mild depression and anxiety in this patient population.

Dr. Sallie Baxendale

"It's noninvasive, inexpensive, and might work."

The study was published online March 21 in the British Journal of Psychiatry.

Common Comorbidity

"Depression is the most common comorbidity of epilepsy," write the investigators.

Dr. Baxendale noted that in her work with people with epilepsy during the past 20 years, the unpredictability of seizures can often be harder to live with than the seizures themselves.

"So it's not surprising that people feel down at times. There is also some recent research that suggests that depression and epilepsy are biologically linked — that the same parts of the brain are involved."

She added that although both depression and anxiety are "very common" in this population, because these people already take many different medications to try to control their seizures, "some are understandably reluctant to take even more pills to try to feel better."

Past studies, as reported by Medscape Medical News, have suggested that light therapy can be effective for treating seasonal affective disorder (SAD) and symptoms of nonseasonal major depressive disorder. The treatment has also been found to be helpful for antepartum depression.

"Bright light therapy, which was originally developed for people with SAD, has been shown to reduce symptoms of low mood in quite a few other patient groups. So it made sense to see if it would work with people who have epilepsy too," said Dr. Baxendale.

For the original study, 101 patients older than 18 years who had medically intractable focal epilepsy and who reported having an average of at least 4 seizures per month were enrolled at a center in London.

All participants were randomly assigned to undergo 20 minutes per morning of either high-intensity, bright light therapy (10,000 lux at 61 cm; n = 51; mean age, 46.6 years) or low-intensity, bright light therapy (2000 lux at 61 cm, n = 50; mean age, 42.9 years).

Anxiety, Depression Decreased

The primary outcome measure, which was reported in a previous publication, was seizure control. This analysis focused on the secondary measures of anxiety and depression.

The study participants completed the HADS at baseline and after 12 weeks of treatment from January 4, 2011, to March 28, 2011. Unfortunately, only 31 of the patients in the high-intensity group and 27 of those in the low-intensity group returned full questionnaires.

Results showed that of those who returned their questionnaires, anxiety scores on the HADS were significantly lower at the end of treatment for both groups (P < .01), as were depression scores (P < .01).

Although the response was greater for both types of symptoms in the high-intensity group vs the low-intensity group, this was not deemed statistically significant.

However, in further analysis, 9 of the 16 patients (56%) in the high-intensity group who had clinical levels of anxiety at baseline reduced their scores to 8 or lower on the HADS at the end of treatment compared with only 2 of the 10 patients (20%) in the low-intensity group. This represented a significant difference in response between groups (P < .05).

Four of the 6 patients (66%) in the high-intensity group with clinical depression at baseline reduced their scores to 8 or lower on the HADS depression scale after 12 weeks of treatment vs 3 of the 7 patients (43%) in the low-intensity group — a between-group difference that was not statistically significant.

There were no significant correlations found between seizure frequency changes and measures of depression or anxiety.

"This is not surprising since it is often the diagnosis of epilepsy itself and the concomitant unpredictability of seizure occurrence that are associated with elevated levels of anxiety and depression in this population, not the number of seizures experienced," write the investigators.

More Research Needed

"At face value, these [overall] results suggest that bright light therapy is no more effective than a placebo in reducing symptoms of anxiety and depression," they add. "However, a number of features in the data suggest that there may be some value in pursuing this line of enquiry further."

They note that although the low-intensity light therapy was supposed to represent the placebo condition, its 2000 lux setting "may have been more powerful than we intended."

Still, "it suggests that light therapy may be an effective treatment of low mood in patients with epilepsy at lower intensities than those typically used to treat SAD," said Dr. Baxendale in a release.

Study limitations cited include the small sample size and the fact that all of the participants reported having frequent seizures.

"The psychosocial and psychiatric characteristics of this population will be different from the majority of people with epilepsy whose seizures are fully controlled by medication. Caution should therefore be employed when generalising the results from this study," write the investigators.

Nevertheless, "the initial findings are encouraging," they add.

Novel Application

Dr. Michael Terman

"This study is promising, although I think some refinement in data analysis could have clarified the results," Michael Terman, MD, director of the Center for Light Treatment and Biological Rhythms at Columbia University Medical Center in New York City, told Medscape Medical News.

"In these small sample studies that are looking at rating scale scores, it's unlikely that you're going to find significant group differences. And this has been true of light studies across the board," he said.

Dr. Terman, who was not involved with this research, noted that instead of focusing primarily on this outcome, the investigators should have focused on the question, "how many people got well?"

"We call this a remission rate as opposed to a score improvement rate, and those for this study are quite promising," he said, citing the 56% vs 20% group rates of anxiety improvement and the "encouraging" finding that 66% of the high-intensity group had depression improvement.

"These are very small samples, but the differences are significant. That means much more to me than the analysis of rating scale scores. And based on that, I'm optimistic that these people are onto an important finding, especially as it relates to epilepsy, which is a novel application of light therapy," said Dr. Terman.

As for other parts of the study, he echoed the investigators' concern over the choice of the 2000-lux setting for the placebo condition.

"It's wrong to assume that their low-intensity condition is inactive physiologically or psychologically. We know that that level of intensity presented at 20 to 30 minutes easily suppresses reduction of melatonin. And that's intimately connected to control of the circadian rhythm phase."

Dr. Terman noted that any antidepressant response to light therapy is caused by 2 major dosing components that were controlled for in this study — intensity of light and exposure duration; and 1 major component that was not controlled for — timing relative to an individual's circadian rhythms.

Nevertheless, "all in all, I think [the investigators] are onto something hot, and I would encourage them to continue with their data analysis," he concluded.

The study was supported by a grant from Action Medical Research. The study authors have reported no relevant financial relationships. Dr. Terman is author of the book, Chronotherapy: Resetting Your Inner Clock to Boost Mood, Alertness, and Quality Sleep.

Br J Psychiatry. Published online March 21, 2013. Abstract