Lack of energy, fatigue and loss of motivation are just some of the symptoms for Seasonal Affective Disorder (SAD). For people who are visually impaired, the risk of developing this form of winter depression is almost three times higher than for people with normal vision.
WHAT IS SEASONAL AFFECTIVE DISORDER?
More than just winter blues, seasonal affective disorder is a type of depression that develops during the same time each year, most often during the fall and winter months. SAD is mostly prevalent for people living in the northern and southern hemispheres where the days are shorter, and the sun goes down sooner.
The main trigger for SAD comes from this lack of sunlight and researchers have come up with a couple of theories on why this happens.[i] They believe that the lack of – or a significant change in the amount of sunlight may upset a person’s biological clock, which controls their sleep-wake patterns.[ii]
Another explanation for SAD could be the disturbance in neurotransmitter functions such as serotonin and dopamine, which are known as the “happy hormones” due to the roles they play in regulating a person’s mood and emotions.[iii] Darkness also increases production of melatonin, which regulates sleep, so when days become shorter, our melatonin production increases leaving us feeling sleepier and more lethargic.[iv]
SAD AND EYE HEALTH
A study published in the British Journal of Psychiatry provides a deeper insight about the frequency of SAD among people who are blind or visually impaired. The study found that a higher proportion of people with blindness or vision impairment suffer from SAD compared to sighted people.
These findings give researchers a reason to believe that the cause of SAD can be found in the retina of the eye, and not in the brain as with other mental illnesses like depression or anxiety.[v]
DEPENDENCY OF LIGHT
During the study, researchers were surprised to learn that a higher proportion of people with vision loss suffered from SAD compared to people who were either completely blind of sighted. The reason behind this is not clear for researcher, however they do believe they found a possible explanation.
They theorize that the cells in the retina that monitor brightness, known as photoreceptors, are crucial for the synchronization of our internal biological clock to light and circadian rhythms. Therefore, people who are visually impaired experience a bigger response in their photoreceptors making them more sensitive to changes in light, despite their poor vision.
On the other hand, people who are blind may not have a conscious perception of light, but researcher argue that there are some cells in the retina that are capable of detecting light that reach the brain. Therefore, people who are blind are less likely to develop SAD than people who are visually impaired.[vi]
OTHER RISK FACTORS OF SAD
Women between 15 and 55 years old are almost 4 times more likely to develop SAD and make up between 60% and 90% of patients who develop the disorder. This is partly due to the fact that women are generally more susceptible to develop depression.[vii]
Darker irises may stimulate more melatonin production, which could make people more vulnerable to SAD. This is because of the amount of light an individual’s eye can process. Usually, eyes with less pigments (blue, green, grey) are more sensitive to light, which means they don’t need to absorb as much their retinal cells to receive and process images.[viii]
Our family medical history is a significant indicator on the likelihood of developing SAD. Any form of depression that is prevalent in our family history automatically increases their chance of developing it.[ix]
Light therapy is one of the most common forms of treatment for patients who suffer from SAD since the 1980s. The idea is to replace the decrease of sunshine in winter by exposing a patient to artificial light on a daily basis. Most typically, light boxes filter out the ultraviolet rays and require 20-60 minutes of exposure to 10,000 lux of cool-white fluorescent light, an amount that is about 20 times greater than ordinary indoor lighting.[x]
Vitamin D supplementation is a great starting point to help treat SAD because patients who suffer from SAD were found with low levels of vitamin D in their blood levels.
Psychotherapy, also known as cognitive behavioural therapy (CBT), is another effective way of treating SAD. The goal is to identify negative thoughts and replace them with positive thoughts along with a technique called behavioural activation. This method seeks to help patients identify activities that are engaging and that bring pleasure to improve their coping with winter.
Finally, certain medication such as Selective Serotonin Reuptake Inhibitors (SSRIs) are used to treat SAD.
Since SAD is seen to present itself with patients who have vision impairment, we at Astorino Eye Center thought it would be particularly fitting to reach out to you all today. Consider making an appointment with us or your general physician!
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