Rethinking the evidence for the winter blues

Seasonal affective disorder (SAD) doesn't hold up as a specific diagnostic entity and it should be excised from the DSM

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Seasonal affective disorder (SAD) no longer holds up as a specific diagnostic entity, experts say, and the term should be retired from the DSM.

Seasonal variations in patients with depression are actually small and the construct doesn’t add much beyond what is already covered by the recurrent subtype of depression, they say.

Introduced into the medical community in the 1980s, the SAD diagnosis applies to individuals who exhibit major depressive symptoms that coincide with specific seasons, typically winter and autumn.

One psychologist who has changed his view on the validity of the diagnosis is Professor Greg Murray from the Department of Psychological Sciences at Victoria’s Swinburne University.

His mind was changed when a small 2004 survey he conducted in Melbourne found only 0.3% of people met the criteria for the condition.

“I, myself, have stopped working in the SAD field. Firstly, because it seems to be rare in Australia, and secondly because I’ve always been sceptical of the entire construct of the disorder,” he said.

Commenting on a large US study which failed to find any link between depression and season or sun exposure, Professor Murray said SAD fitted into our folk beliefs that winter was a gloomy time and summer a happy time.

The cross-sectional US study, published last month, took a sample of 34,000 US adults, and analysed data from 1800 who scored in the depressed range on a validated scale.

Despite the entrenched folk theory that depression worsens in winter, the study found no link between depression and sunlight hours or season.

The research also seems to debunk another folk psychology idea that latitude was linked to depression, finding no support for the notion that people who lived closer to the poles experience more depression in winter months.

The findings cast serious doubt on the legitimacy of major depression with a seasonal variation, and it may be time to discontinue this as a diagnostic modifier of major depression, the authors wrote.

“We have to be very careful about trusting patients’ self-beliefs,” Professor Murray said. “A lot of SAD research is not on behaviours but based on retrospective reports asking ‘what time of year do you feel worse?’”

In contrast, his own longitudinal research surveyed participants about their current mood, and found seasons had a very small effect, less than events such as getting a parking ticket or having a fight with a spouse.

It might be normal for many people, even if not depressed, to have mood alterations in winter, he said. Winter correlates with other things that might decrease mood, such as being less active, socialising less, or putting on weight, Professor Murray told The Medical Republic.

“For example, in winter in Melbourne you might do less exercise, put on some weight or socialise less and this may lead to a very small average decrease in mood.”

For patients who said they felt worse in winter, Professor Murray advised considering a diagnosis of recurrent depression. He advised exercising regularly during winter, maintaining a social life, and refraining from blaming themselves if they were sleeping more or putting on weight.

However, a positive thing to come out of the exploration of SAD was the development of light therapy as a treatment for depression, he noted.

“Light is an effective treatment for depression with a seasonal variation… and so is Prozac. “But vice versa, non-seasonal depression responds to light as well. So those two things together raise doubts that the seasonal variation type [of depression] is a specific entity.”

Associate Professor Trevor Norman, a psychopharmacologist in the Department of Psychology at the University of Melbourne, is also sceptical of SAD a separate logical entity.

Professor Norman conducted one study in which bright-light therapy appeared to help some of those with self-reported SAD, but the patients did not have consistent seasonal patterns, and sometimes had incidences of depression in summer and spring.

“[Also] in theory if there really was a seasonal distinction, those patients with seasonal affective disorder should respond to specific treatment, but they don’t,” Professor Norman said, referring to light therapy and antidepressants being beneficial for both.

While SAD treatment would also seem to require bright-light therapy in the early morning or evening to replicate summertime light patterns, research had shown that it did not matter when it was given, he said.

Importantly, Professor Norman cautioned that a fundamental difficulty with conducting research into bright-light therapy was the difficulty in finding a control therapy to test against.

“Bright-light therapy does seem to work for some people, but that may very well be a placebo,” Professor Norman said. “And if you’ve just paid $300 for a box then you’d really hope it works.”

While it might be diverting patients away from seeing a clinician for their problems, the therapy itself had almost no side effects, potentially only headaches, he said.

However, bright-light therapy had a legitimate place for the treatment of patients who had circadian rhythm disorders and were sleepy by day and wakeful by night. Light therapy could reset the circadian rhythm, and could also work for depressed patients suffering from this kind of disturbance.

The initial enthusiasm for the concept of SAD most likely came from observing patients with undiagnosed bipolar disorder, he said.

“There’s a fairly robust finding about patients with bipolar disorder who have seasonal changes, with seasonal spike of admissions of mania in the spring,” he said.

For his part, Professor Philip Boyce, professor of psychiatry at the University of Sydney, believes some people legitimately suffer from mild seasonal variation of depression, but this is not as common as people thought.

Professor Boyce agreed that in some cases, a seasonal variation in mood might be an early manifestation of bipolar disorder.

“[These patients] have a higher risk of becoming unwell, and that can guide clinical practice and you can start a treatment early.”

Clinical Psychological Science 2016; online Jan 19