Is seasonal affective disorder just a myth? Study finds no evidence it really exists

    21 January 2016

    There is no evidence that levels of depressive symptoms vary from season to season, according to research published in Clinical Psychological Science.

    The results of the study (a large-scale survey of US adults) are inconsistent with the notion of seasonal depression as a commonly occurring disorder.

    Steven LoBello, the study’s senior author, said: ‘In conversations with colleagues, the belief in the association of seasonal changes with depression is more-or-less taken as a given and the same belief is widespread in our culture. We analysed 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.’

    Patients with seasonal affective disorder (SAD) report recurring depressive episodes that coincide with specific seasons — in most cases, an increase of symptoms in winter and a decrease in summer.

    But recent studies have challenged the validity of earlier SAD research, including the fact that SAD is typically identified by asking patients to recall past depressive episodes over the course of the previous year or more. Furthermore, the criteria used to identify SAD do not align with the established criteria for major depression.

    LoBello and lead study author Megan Traffanstedt decided to investigate whether they could find evidence for seasonal variation in depressive symptoms.

    The researchers examined questionnaire data from 34,294 participants and, using geographical location data for each participant, were able to measure the amount of sunlight exposure each patient experienced.

    The results showed no evidence that symptoms of depression were associated with the time of year, or any evidence for seasonal differences in patients with clinical depression.

    ‘The findings cast doubt on major depression with seasonal variation as a legitimate psychiatric disorder,’ the researchers conclude. They argue that ‘being depressed during winter is not evidence that one is depressed because of winter’.

    LoBello said: ‘Mental health professionals who treat people with depression should be concerned about their own and their patients’ accurate conceptions about the possible causes of depression. Pursuit of treatments based on false causes is unlikely to lead to rapid and durable recoveries.’

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