A study from Denmark shows being blind or visually impaired increases your risk of seasonal affective disorder.
Vision and Seasonal Affective Disorder: An Interview with Helle Madsen, MD
Helle Madsen, MD, of the Mental Health Services Copenhagen, University of Copenhagen, Denmark, recently presented a poster at the American Psychiatric Association’s annual conference in Atlanta, Georgia, USA. CET asked Dr. Madsen a few questions about her findings.
CET: Dr. Madsen, you and your colleagues recently reported that seasonal affective disorder (SAD) was extremely common in people who are visually impaired.
Dr. Madsen: Yes, we found that totally blind people were twice as likely to have SAD as the average person, and people who had greatly reduced sight were three times as likely to have SAD.
CET: Why is that?
Dr. Madsen: Light striking the retina directly affects mood, and circadian rhythms. In persons with severe visual impairment, the pathway of light input is interrupted in varying degree so that not enough light reaches the brain to maintain normal mood and energy levels. Studies in SAD patients suggest that their retinas are less sensitive to light. This subsensitivity has been shown for both rods and cones, and the intrinsically photosensitive retinal ganglion cells.
CET: How did researchers find that out?
Dr. Madsen: We looked at people who had problems with vision early in life, including individuals who are born blind. These individuals with early vision problems had fewer symptoms of SAD than people who develop eye conditions later in life.
The retina has with two types of photoreceptors for vision: rods, which cannot detect color, and cones, which can. Courtesy of the National Eye Institute, National Institutes of Health
CET: Why is that?
Dr. Madsen: We do not know, but we hypothesize that the brain sets the threshold for necessary light input at a lower level if you are born with an eye disorder. This effect makes visually impaired persons born with normal sight vulnerable to SAD ― more vulnerable than they would be if their visual systems had only been exposed to lower light levels in the first place.
CET: Any other findings?
Dr. Madsen: We also discovered that people with macular degeneration ― which starts with blurred or no vision in the center of the visual field ― have increased symptoms of SAD.
CET: Would these individuals, or anyone with visual problems, benefit from light therapy if they had seasonal affective disorder?
Dr. Madsen: We don’t know, but it is very possible. Our findings suggest that they are still somewhat sensitive to changes in light conditions, and therefore possibly able to benefit from light therapy. I also think it is important to inform persons with visual impairment of the importance of increasing their light exposure as much as possible during winter. It they are not too photosensitive, they should open their eyes, and not wear sunglasses when outdoors.
CET: What implications might your work have for how health professionals treat people with visual impairments?
Dr. Madsen: If a person presents with depressive symptoms in relation to a complete or partial lack of sight, I think it is important to consider whether there is a seasonal pattern and if so increase light exposure and attempt light therapy.
CET: Thank you, Dr. Madsen