Answer: The 6-month instruction can be adjusted to suit the interval being used. If the interval is shortened much below 6 months, this may slightly reduce scores on some problem items and scales. Low-frequency behaviors may also be missed if the rating interval is too short. However, if reassessments are planned at intervals of less than 6 months, respondents should use the same shortened interval for the initial ratings as well as for each follow-up rating. For example, if follow-up ratings are to be done after a 4-month interval, the initial rating should also be based on a 4-month period, so that the initial scores will not be higher than the follow-up scores merely because they span a longer rating period. To allow time for changes to stabilize and to become clearly evident, reassessment intervals should generally span at least a month.