Seasonal affective disorder refers to a seasonal fluctuation in depressive symptoms. Although currently accepted by medical professionals, a new large-scale study asks whether it truly exists.

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New research brings seasonal affective disorder into question.

Seasonal affective disorder (SAD) was officially added to the Diagnostic and Statistical Manual of Mental Disorders (DSM) in 1987.

As such, it is a relative newcomer to the psychiatrist’s lexicon. However, the effect of the seasons on mood has been part of folk psychology for generations.

The idea that light and dark phases have an impact on psychological outlook was mentioned millennia ago by Aretaeus of Cappadocia; he said:

“Lethargics are to be laid in the light, and exposed to the rays of the sun, for the disease is gloom.”

More modern discussions and studies, in the late 1970s and 1980s, brought attention to SAD and cemented its place in modern psychiatry. For now.

Today, SAD is not considered a stand-alone condition, rather a specifier to describe subsets of major depressive and bipolar disorders.

In short, a depressed patient with SAD has recurrent depressive episodes during the winter season. Conversely, individuals with SAD show marked improvements in mood during the warmer months.

At least, that is how SAD has been described until recently. Over the last few years, a number of researchers have called into question whether SAD is a valid diagnosis.

Some of the earlier research that brought scientific attention to SAD has been, at least partially, discredited. Much of the information regarding seasonal variation in depressive symptoms was gathered by asking participants to recall past depressive episodes that spanned a year or more.

New research, published in Clinical Psychological Science, reopens the case and takes a fresh look at SAD.

Conducting a large-scale survey across the US, the research team used data taken from a phone-based health survey in 2006 as part of the Behavioral Risk Factor Surveillance System. In all, data from 34,294 individuals was used, ranging in age from 18-99.

Depressive symptoms were evaluated using a validated measure known as the PHQ-8. The number of days on which depression had been experienced were charted for the 2 weeks prior to the interview. Of the questionnaire’s respondents, 1,754 were classed as clinically depressed.

The data included geographic location, enabling the researchers to precisely define the participant’s latitude and the quantity of sunlight at their given location for the specific time of year.

Controversially, when the data was analyzed, no seasonal variation was found. Prof. Steven LoBello, senior author and professor of psychology at Auburn University at Montgomery, said:

We analyzed the data from many angles and found that the prevalence of depression is very stable across different latitudes, seasons of the year, and sunlight exposures.

The findings cast doubt on major depression with seasonal variation as a legitimate psychiatric disorder.”

Depression is, by its very nature, episodic. Symptoms wax and wane. This means that a depressed patient is likely to suffer episodes during some winters but also during some summers.

“Being depressed during winter is not evidence that one is depressed because of winter,” write the authors.

No doubt these findings will spark lively debate. SAD has been resident in the DSM for decades. Although the study is the largest of its type, there will undoubtedly be a backlash from patients with a SAD diagnosis and from researchers in the field.

Alongside the inevitable debate, there is guaranteed to be more research. It is only additional studies that will eventually prove SAD’s existence or lack thereof.

Medical News Today recently wrote about beating the winter blues with cognitive behavioral therapy.