Prevalence of seasonal affective disorder in primary care; a comparison of the seasonal health questionnaire and the seasonal pattern assessment questionnaire.
BACKGROUND
Prevalence rates of SAD suggested by previous studies have ranged from 1 to 12% depending on the diagnostic criteria used. The Seasonal Pattern Assessment Questionnaire (SPAQ), a widely used screening tool, has been shown to have low specificity for SAD. The Seasonal Health Questionnaire (SHQ) was designed to better reflect the clinical criteria for SAD and has been shown to have a higher specificity then the SPAQ in a psychiatric outpatient setting.


OBJECTIVE
The current study was designed to assess the validity of the SHQ in general practice against systematic research interviews, to compare the sensitivity, specificity and positive predictive values of the SHQ and the SPAQ and to use these data to estimate the prevalence of SAD in primary care.


METHODS
809 subjects in a consecutive series of patients attending Southampton general practices in winter 2000/01 completed the SHQ followed by the SPAQ; 56 were interviewed using the Structured Clinical Interview for DSM (SCID).


RESULTS
The SHQ was more sensitive and specific than the SPAQ and had higher positive and negative predictive values in screening for SAD. The SPAQ indicated a prevalence of SAD of 10.7% (95% CI 8.6-13.1) while the SHQ provided a significantly lower estimate of 5.6% (95% CI 4.2-7.4).
Thompson
Chris
C
Community Clinical Sciences Research Division, University of Southampton, Royal South Hants Hospital, Brinton's Terrace, Southampton SO19 4YP, UK. ct1@soton.ac.uk
Thompson
Susan
S
Smith
Rachel
R
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D011237:Predictive Value of Tests; D015995:Prevalence; D011320:Primary Health Care / Q000706:statistics & numerical data*; D016574:Seasonal Affective Disorder / Q000175:diagnosis* / Q000453:epidemiology*; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires / Q000592:standards*