Pretreatment attrition in a comparative treatment outcome study on panic disorder.

OBJECTIVE

Whereas the fact of attrition during the course of treatment is well documented, little is known about the factors that affect sample selection before the beginning of a study ("pretreatment attrition"). The present study reports on the degree and sources of pretreatment attrition at two sites of a multicenter study on panic disorder that compared treatment outcomes for imipramine and cognitive behavior therapy.

METHOD

Data were collected at two clinical research sites, one with a pharmacological treatment orientation (N = 420) and one with a psychosocial treatment orientation (N = 208).

RESULTS

The main source of pretreatment attrition was participant refusal. At both research sites, eligible patients most often refused participation because they were either unwilling to start treatment with imipramine (30.6% and 47.4%, respectively) or discontinue their current medication (22.6% and 35.1%, respectively).

CONCLUSIONS

Results from comparative treatment outcome studies are limited not only to people who meet the study criteria but also to those who are willing to begin a medication treatment and discontinue their current medication.