- The likelihood of winter blues and depression far outweighs the experience in summer, and the clinical picture is very different.
- Most but not all cases of winter depression are accompanied by fatigue, food craving, weight gain, and increased sleep.
- The crash can be avoided by starting light therapy when noticing increased appetite or difficulty rising from bed.
Seasonal Affective Disorder (SAD), has been defined both too broadly and too narrowly. How can that be? On the one hand, the Diagnostic and Statistical Manual of Mental Disorders (DSM) is neutral about which season triggers depression, even though about 9 out of 10 people show annual mood worsening in winter, not summer.
Winter depression is marked by excessive sleepiness, food cravings, and weight gain, summer depression by insomnia and reduced appetite. Winter treatment focuses on light therapy, which counters the darkness with earlier, artificial sunrises. There is no clear-cut remedy for the rare summer depression. The two seasonal patterns are not mirrored images, and it is confusing to lump them together. The DSM definition of SAD is too broad.
On the other hand, it is also too narrow!
For winter depression to fit the DSM definition, seasonal episodes must substantially outnumber non-seasonal episodes over the years. At the time of diagnosis, however, the last two winters must both have been symptomatic. Someone who skipped becoming depressed last year, but became depressed again this winter, cannot officially receive a diagnosis of seasonal pattern even if the depressions have occurred in winter more often than not. This requirement, therefore, ends up excluding many seasonal cases that would be responsive to light therapy.
Indeed, winter depression does not necessarily occur every year, but it occurs regularly enough over the long term to outweigh depressive episodes in other seasons. Some years it may feel like the winter doldrums or occur in brief recurrent bouts short of full-blown depression, while other winters may pass without difficulty.
A Multiplicity of Symptoms
In deciding whether to begin light therapy, one should consider a set of key symptoms that predict treatment success:
- Hypersomnia (sleeping far longer than usual)
- Energy slumps in the afternoon or evening, which improve before bedtime
- Feeling worse overall in the evening than morning
- Craving carbohydrate-rich foods (unlike in summer)
- Eating more and gaining weight
When some or all these symptoms are present, it’s a good bet that light therapy will eradicate the depression even when the DSM criteria have not been met.
To sharpen our understanding of SAD, it is helpful to identify the potential population of light therapy responders in all its variations.
Seasonality in the General Population
To estimate population prevalence of SAD, a Swiss study administered DSM interviews for major depression, along with a seasonality questionnaire, to nearly 1000 adults, 29-89 years old, which formed a representative population sample. They were asked to rate the severity of winter changes in both psychological and body symptoms, from “absent” through mild, moderate, and severe. As expected, the large majority did not experience winter depressions, but 11% did.
Unsurprisingly — as the graphic summary shows — these pronounced seasonal cases showed large, orderly swings between winters worse and summers much better. As psychological wellbeing approached its low point at the start of winter, the body symptoms — hypersomnia, heightened appetite, and weight gain — swung upward. And with the onset of spring, the trends reversed.
The surprise was that the larger group without seasonal depression showed nearly the same pattern, but the winter-summer swings were far less prominent. Milder swings in psychological state and body symptoms are thus normal seasonal changes. When these symptoms become bothersome, light therapy can also help.
Winter Symptoms Without Depression
Now consider a group of people who experience the characteristic body symptoms of SAD — lower energy, need for more sleep, a bigger appetite, and eating more — but without feeling depressed! They do not have a mood disorder, and clinical trials are still needed to investigate the usefulness of light therapy.
This non-depressed seasonal group is essential for understanding SAD because the physical symptoms appear around a month earlier than the mood symptoms at the start of the depressive episode. This sequence in the seasonal timeline is beneficial information for those with SAD because they can anticipate the plunge into depression weeks later and start preventive light therapy before it happens. By detecting the need for more sleep, or onset of food craving as precursors of the mood episode, they can begin light therapy early and avoid the winter episode altogether.
Winter Depression With Insomnia and Low Appetite
Finally, consider a relatively small group of seasonal patients who relapse into winter depression without the associated sleep and appetite symptoms. Unfortunately, the likelihood that they will respond to light therapy is significantly lower than those with anticipatory symptoms. Experience treating this variant of winter depression is still quite limited, and the likely recourse is standard antidepressant medication until the winter passes.
These variations in seasonal symptom patterns lead us to view the cycle of sleep and appetite symptoms as distinct from the depression itself yet linked to it by anticipatory timing. Watch out for that carbohydrate craving late at night! It’s a first sign that winter depression is likely on its way.
SAD and COVID-19 Isolation: A New Relationship
In another scenario, the pressure for a long sleep, increased appetite, weight gain, and blue mood have emerged apart from the seasons, courtesy of COVID-19 isolation.
Stuck at home for weeks on end, in-room light that never matches what we find outdoors, we are denied the natural seasonal lighting conditions that ward off winter depression, even in spring and summer. Light therapy upon morning waking both stabilizes the circadian sleep-wake cycle and counteracts the lassitude of indoor life.
Appropriately self-administered light therapy can ward off depression at any time of year, even for people who have never experienced seasonal mood cycles in everyday daily life. Alternatively, if possible, half an hour outdoors every morning is a naturalistic treatment variant.