Page 332 - Zumtobel Group Geschaeftsbericht 2013-14 EN

Basic HTML Version

results Magnusson concludes that “the construct va-
lidity of the SPAQ was supported”. But based on the
data in this study, one could make an equally strong
argument for the SPAQas an instrument for identifying
seasonal anxiety disorder as for seasonal affective
disorder. What Magnusson’s study really demon-
strates is that the SPAQ can be used to identify sub-
jects with a high level of mental distress who feel
worst during the winter months, regardless of the
type of distress.
In the only University of Tromsø study that used the
SPAQ, in a population living at 70 degrees north, the
same sample was measured at four different times
during one year (Lund & Hansen, 2001). The preva-
lence of SAD varied between 5.6% and 14.4%. The
highest prevalence of SAD was reported in March,
when day and night are of equal length and no lack
of daylight is experienced in northern Norway.
Even in June, the prevalence of SAD was higher than
in dark January. Our interpretation of these findings
is that the SPAQ does not measure peoples’ general
response to the season, as it purports to do. Instead,
SPAQ scores are probably heavily influenced by
weather conditions at the time of completion. In
March 1997, there was an extreme blizzard for
several days during data collection. Thus, one of the
explanations for differences in prevalence of SAD in
SPAQ studies could be widely differing weather
conditions at the time the studies were performed.
Very few studies report what time of year the data
were collected, much less the current weather condi-
tions, making comparisons between studies of rather
limited value.
To sum up: the SPAQhas very serious methodolog-
ical flaws, with low test-retest reliability, low sensitivity
and low predictive validity, and it seriously overesti-
mates the prevalence of seasonal depression. Because
most research in the field employs the SPAQ, we actu-
ally know very little about seasonal depression.
Instead we know quite a lot about a condition which
this author proposes to call “SPAQ-iasis”, a condition
you have if you score above a certain threshold on
the SPAQ. “Seasonal Affective Disorder” is nothing
more than a “SPAQ-iasis”, a constructed disease. The
DSM diagnostic entity “Major Depressive Disorder
with seasonal pattern” seems to be more valid. But
even if some people have depressive episodes that
tend to recur at about the same time of the year, the
value of placing such a syndrome in a separate diag-
nostic category is highly questionable, particularly if
the recommendations for treatment are the same for
non-seasonal and seasonal depression.
Extensive use of the concept of Seasonal Affective
Disorder, and of the instrument to measure it, the
SPAQ, has led to great confusion in the study of pos-
sible connections between depression and seasonal
changes in light and climatic conditions, since the
concept does not correspond to the definition of recur-
rent depression with seasonal pattern in the DSM-IV
or the ICD-10 diagnostic classification systems. Even
these definitions have a rather weak research base,
and should still be regarded as provisional.
A closing story
I met Norman Rosenthal at an international congress
on winter depression arranged by the University
of Tromsø in January 1997. He was excited by the
opportunity to experience the dark winter, and he
hoped to better understand why northern Norwegian
scientists had not discovered winter depression long
before he did. During the congress, the weather was
clear, therewas ametre of pristine snowon the ground,
and the northern lights flashed across the sky. On his
return, he was somewhat self-critical in his new book
Vidje Hansen
Does sparse variation of ambient light
in winter cause depression?