What is this thing called "SAD"? A critique of the concept of Seasonal Affective Disorder.
BACKGROUND
Seasonal Affective Disorder (SAD) is supposed to be caused by lack of daylight in winter. Yet the population of Northern Norway, living without sun for two winter months, does not spontaneously complain about depression during the dark period.


OBJECTIVE
To summarize research bearing upon the validity of the concept of SAD.


METHODS
Review of relevant literature concerning the epidemiology of SAD and the questionnaire developed to measure it in general populations, the Seasonal Pattern Assessment Questionnaire (SPAQ).


RESULTS
Large population studies from northern Norway do not point to a higher prevalence of depression in winter than expected in any other general population. The psychometric properties of SPAQ are rather poor, and the diagnosis of SAD based on SPAQ bears little relationship to a meaningful concept of depression.


CONCLUSIONS
Seasonal Affective Disorder is not a valid medical construct. Instead, "Recurrent depression with seasonal pattern" as defined in the DSM-IV and the ICD-10 should be used as terms. However, more research is needed to establish whether it is at all fruitful to single out such a subtype of recurrent depression.
Hansen
Vidje
V
Institute of Clinical Medicine, University of Tromsø, Norway. vidje.hansen@unn.no
Skre
Ingunn
I
Lund
Eiliv
E
D006801:Humans; D016574:Seasonal Affective Disorder / Q000175:diagnosis / Q000188:drug therapy / Q000523:psychology; D011795:Surveys and Questionnaires