Exposure definition
All three studies had national prescription registries as source of
their exposure data. Study 1 considered women as exposed to HC if having
a valid prescription within the last six months prior to either use of
antidepressants or getting a depression diagnosis. Study
22 considered a valid prescription of HC as being
exposed. Study 33 considered a valid prescription of
HC within the first four weeks after prescription as non-use, so that
women were considered users of HC from four weeks after starting use of
HC. The argument was that women could not develop a depression or start
use of antidepressants due to use of HC so quickly after starting this
use.
Study 1 and 2 followed women from they started using HC, whereas study 3
examined current users (Table 2).