I appreciate the opportunity to address the diagnostic issues raised by Swinson and Cox about our twin study. 1 Our criteria for GAD were based on the July 1, 1985, version of the Structured Clinical Interview for DSM-III-R (SCID).2 At that time in the revision of DSM-III, GAD criteria had not yet taken their final form. As a result, the SCID questions on GAD reflected, in important ways, DSM-III rather than DSM-III-R criteria. Our interview required a period in which the individual reported being "anxious, nervous, or worried more days than not." Unlike the SCID, which required a minimum duration of 6 months, we used a minimum duration of 1 month or greater but subsequently asked for the longest duration of an episode so that we could reconstruct the minimum 6-month duration. The interview did not assess whether these anxious or nervous feelings were related to two or more
Kendler KS. Diagnostic Validity in Genetics Research on Generalized Anxiety Disorder-Reply. Arch Gen Psychiatry. 1993;50(11):916–917. doi:10.1001/archpsyc.1993.01820230086009
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