Some clients are short term, and others are long term. Short-term clients tend to be rapid responders or early dropouts; long-term clients fi nd progress more diffi cult to achieve.

Although most of the research is on adults and has signifi cant limitations, there appears to be a subgroup of clients who make progress early in treatment (averaging at the fi ft h session), which accounts for much of their total improvement. For instance, in a study of a 16-session manualized cognitive-behavioral treatment for depression, 39% of those who completed treatment showed a pattern of early sudden gains, which accounted for half the total improvement they reported at termination (Tang & DeRubeis, 1999). In another study, depending on the criteria used to defi ne “sudden gain,” 17% to 56% of the 135 clients who completed treatment in three clinics in England were found to have made early sudden gains that accounted for all the improvement they reported at the end of therapy (Stiles et al., 2003).