You are not alone if colder climate and longer nights make you are feeling down. This well-known phenomenon, referred to as seasonal affective dysfunction (SAD), may clarify why individuals really feel low, irritable, and torpid within the winter months. For some, the situation will be critical and debilitating.
Though SAD is a recognised type of medical despair, consultants are nonetheless divided on what causes the situation, with some even arguing it does not exist. However my very own analysis has discovered that your eye color may truly be one issue figuring out whether or not or not you develop SAD.
A survey I performed in 2014 discovered that round eight % of UK individuals self-reported adjustments with the seasons that may be labeled as SAD.
One other 21 % reported signs of sub-syndromal SAD, which is a much less extreme kind, typically referred to as the “winter blues”.
Although many individuals may suspect they’ve SAD, the situation is normally recognized utilizing the seasonal sample evaluation questionnaire. This asks individuals to reply various questions on seasonal behaviour, temper and behavior adjustments.
The upper individuals rating on the questionnaire, the extra critical their SAD is. Nonetheless, these diagnostic instruments might differ between organisations, which may generally result in inconsistent diagnoses.
However what truly causes SAD continues to be debated. Some theories, just like the latitude speculation, recommend SAD is triggered by decreased publicity to daylight throughout the winter.
This means that SAD must be extra frequent in international locations which can be farther from the equator (akin to Iceland).
Nonetheless, various research have did not help this idea. One other idea suggests SAD occurs when our circadian rhythm is disrupted as the times develop shorter.
Different theories suggest it occurs attributable to an imbalance in serotonin and melatonin within the physique. Serotonin makes us really feel energetic, whereas the discharge of melatonin makes us really feel sleepy.
Since melatonin is constituted of serotonin, individuals with SAD might probably produce an excessive amount of melatonin throughout the winter months, leaving them feeling torpid or down.
All these research are inconsistent and, in some instances, contradictory. However as a result of SAD is probably going attributable to a mix of many organic and physiological elements working collectively, these totally different explanations for what causes SAD could be interconnected.
SAD and your eye color
We’ve got uncovered proof that an individual’s eye color can have a direct impact on how prone they’re to SAD.
Our examine used a pattern of 175 college students from two universities (one in south Wales, the opposite in Cyprus). We discovered that individuals with gentle or blue eyes scored considerably decrease on the seasonal sample evaluation questionnaire than these with darkish or brown eyes.
These outcomes agree with earlier analysis which discovered that brown or dark-eyed individuals had been considerably extra depressed than these with blue eyes.
The rationale that eye color might make some individuals extra prone to despair or temper adjustments could be due to the quantity of sunshine a person’s eyes can course of.
The retina is the a part of our eyeball containing cells which can be delicate to gentle. When gentle enters the attention, these cells set off nerve impulses that kind a visible picture in our mind.
In 1995, scientists found that some retinal cells, moderately than forming a picture, merely ship details about ranges of brightness from the again of the attention to the mind’s hypothalamus.
The hypothalamus is a crucial a part of the mind which secretes hormones (akin to oxytocin) that regulate temperature, starvation and sleep cycles.
As the quantity of blue and inexperienced gentle reaching the hypothalamus will increase, the quantity of melatonin decreases. Eyes with decrease pigment (blue or gray eyes) are extra delicate to gentle.
This implies they needn’t take up as a lot gentle as brown or darkish eyes earlier than this data reaches the retinal cells.
As such, individuals with lighter eyes launch much less melatonin throughout the fall and winter. This mechanism may present light-eyed individuals with some resilience to seasonal affective dysfunction (although a smaller proportion should still expertise SAD).
Two theories have historically been used to elucidate why blue eyes happen in Western populations dwelling farther from the equator. First, it could be seen as extra engaging to the alternative intercourse, so it’d present a reproductive benefit.
Second, blue eyes could also be a facet impact of the identical mutation that causes lighter pores and skin color. This mutation developed as a result of it helps the physique make extra vitamin D from the solar’s ultra-violet gentle in components of the world that obtain much less radiation, particularly throughout the winter.
However provided that blue-eyed individuals in our examine reported decrease ranges of SAD than their brown-eyed counterparts, this mutation might have occurred as an “anti-SAD” adaptation because of the appreciable variations in gentle publicity that our prehistoric ancestors skilled as they migrated to northerly latitudes.
Eye color is, after all, not the one issue right here. Individuals who spend too lengthy indoors are additionally extra prone to each winter blues and full-blown SAD.
Happily for these with SAD, merely going exterior for a daily stroll, particularly at instances when it is sunny, will assist enhance their temper.
If that does not work, “phototherapy”, which includes sitting in entrance of a light-weight field for an hour every day, might additionally assist. Folks I’ve suggested to make use of these strategies (whether or not brown or blue eyed) nearly invariably have reported a noticeable enchancment.
Nonetheless, individuals with SAD are suggested to seek the advice of a GP regardless, particularly if their signs don’t enhance, or if the situation turns into tough to handle.
Lance Workman, Visiting Professor in Psychology, College of South Wales.
This text is republished from The Dialog beneath a Inventive Commons license. Learn the unique article.