Seasonal Affective Disorder

A conversation about Seasonal Affective Disorder usually brings to mind the idea that low light levels are the main cause of this condition. Too often, scientific studies in an attempt to simplify the process, will isolate one or two factors as causal but this approach almost always falls short. 

Seasonal Affective Disorder or SAD can affect anyone.

Most health conditions are caused by a number of factors and the tendency to be reductionistic prevents us from understanding what the other potential causes are. SAD is one of those examples. When patients ask what are the causes of a particular disease or condition my answer is usually “a combination of genetics and environment.” If we believe that genetic and environment usually play a role in these processes and we apply this to SAD, we could say that the causes of SAD in some individuals are multifactorial. In order to understand what some of those factors are, I began investigating and this is a brief summary of what I found:

It’s a subtype of Depression

Seasonal Affective Disorder or SAD can affect you all year long.

Seasonal Affective Disorder (SAD) is considered to be a subtype of major depression showing the following symptoms according to the National Institute of Mental Health:

  • Feeling depressed most of the day, nearly every day
  • Feeling hopeless or worthless
  • Having low energy
  • Losing interest in activities you once enjoyed
  • Having problems with sleep
  • Experiencing changes in your appetite or weight
  • Feeling sluggish or agitated
  • Having difficulty concentrating
  • Having frequent thoughts of death or suicide.

Seasonal Affective Disorder can happen at any time of the year

There are two patterns of SAD, one that presents in the winter time, and one that is much less common and presents in the summertime.

Seasonal Affective Disorder or SAD can affect you no matter where you live.

Symptoms of the winter pattern of SAD include:

  • Having low energy
  • Hypersomnia
  • Overeating
  • Weight gain
  • Craving for carbohydrates
  • Social withdrawal (feel like “hibernating”)

Symptoms of the less frequently occurring summer seasonal affective disorder include:

  • Poor appetite with associated weight loss
  • Insomnia
  • Agitation
  • Restlessness
  • Anxiety
  • Episodes of violent behavior

Risk factors for Seasonal Affective Disorder

The NIH website says that young females, living further away from the equator with a family history of depression or bipolar disorder have higher risk factors for SAD. With that said, any demographic can be affected. Contributing factors for SAD may include lower amounts of free serotonin in the synapse, overproduction of melatonin, and people who test positive for lower levels of vitamin D3. It appears that dopamine or efficacy of dopamine reaching its receptor can also play a role in SAD, although the cause is not well understood and it doesn’t seem to be associated with low levels of light2.

As Levitan explains,“Converging evidence also points to a role for the major monoamine neurotransmitters serotonin, norepinephrine, and dopamine in one or more aspects of SAD.” Central and peripheral levels of these neurotransmitters along with GABA and acetylcholine are in constant flux, so it would not be surprising that we might observe changes in these levels during a significant shift in circadian rhythms and in the environment we live in. Again, Levitan proposes that SAD is likely caused by a complex set of factors that are influenced by genes unique to each factor including biological rhythms, mood regulation, appetite and light sensitivity.

It can be said then, that SAD in winter is the body’s maladaptive response to changes in circadian cycles that include very low levels of light, and cold temperatures that stimulate changes in feeding behavior. Interestingly, few studies have addressed the role of cold weather and precipitation as contributing factors to SAD.

Why is Seasonal Affective Disorder so poorly understood?

Seasonal Affective Disorder or SAD can affect you all year long.

The progress of research on this condition is pretty slow in part because it is a subset of depression and to be very frank, research gets done when the prospect of financial gain is high. Since SAD is a complex process, the diagnostic process is difficult and research may not be able to provide an easy target for monotherapy.

Given that this is a complex disorder, here are a few contributors to SAD that I think deserve more attention than they get:

Low vitamin D3 levels – Yes, even the research shows that low levels of vitamin D3 in the body correlate and likely contribute or cause some portion of SAD, but people blow it off like it’s not that important. We hear about it, we talk about it but most people in northern climates don’t get enough of it and it affects their health in dramatic ways.

Maladaptive response to low levels of light – This is another article, and perhaps a long one. We know that low light can contribute to physiological changes in melatonin, cortisol and many other neurotransmitters. But it is appalling how understated this problem is. The difference of our exposure to light between a sunny day and a brightly lit building is incredible.

Maladaptive response to cold temperatures – I haven’t researched this yet but I can imagine there is a physiological response to temperature extremes and a psychological effect resulting from to maladaptive response to the change. This may explain why people migrate south for winter. I know of one article that shows a map that the author called a “Dreariness Index based on total precipitation, # of wet days and light levels but he didn’t include temperature.

Maladaptive response to precipitation –  I’ll talk more about weather and its contributions to SAD in another article but I live in a very wet climate and I can tell you that people have a difficult time adapting to precipitation, and as I mentioned with the cold weather, maladaptive responses can affect the psyche of an individual.

Neurotransmitter imbalance – Biochemistry is determined genetically and is highly influenced by our environment. We need to do more research to help us understand how to apply lifestyle changes and nutrient therapy to correct these imbalances so that people can live happier, healthier lives.

Sex and stress hormone imbalance – Again, genetics and environment influence hormone levels and when imbalance occurs, the whole body will be affected.

So what can you do?

First off, as with any of these symptoms, if you suspect you are suffering from any mental condition including depression, you need to seek medical attention from a qualified healthcare provider before beginning a treatment plan of any kind.

If you, like millions of others, are feeling that general tiredness, malaise and dissatisfaction that we listed above… especially now that we are in the dead of winter. The FIRST thing I’d do is start supplementing Vitamin D3. Everyone that lives in the northern hemisphere should likely be adding this to your daily diet. We have a fantastic high potency formula that we love and we sell it directly on our site.

If you feel like you want a more well rounded approach to total brain balance; check out our EQ formula and see if it sounds like something for you!

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1.The chronobiology and neurobiology of winter seasonal affective disorder Robert D. Levitan, MD; FRCPC; MSc*.

2. Dopamine and light: dissecting effects on mood and motivational states in women with subsyndromal seasonal affective disorder

Elizabeth I. Cawley, MSc, Sarah Park, MSc, Marije aan het Rot, PhD, Kimberley Sancton, BSc, Chawki Benkelfat, MD, DERBH, Simon N. Young, PhD, Diane B. Boivin, MD, PhD, and Marco Leyton, PhD


4. SAD definition:


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