In order for the treatment of depression to be most effective people need to keep taking their medication and stay in contact with therapists and clinicians. Unfortunately many people drop out of their treatment ; something researchers call attrition. An American study looked at 4,041 people being treated for depression with a drug called Citalopram. They found there was an overall dropout rate of 26%. Of those people who dropped out of treatment 34% dropped out immediately, 59% dropped out by week 12 and 7% dropped out after 12 weeks. Immediate attrition was linked to younger age, less education and being less severely depressed. Dropping out of treatment later was associated with younger age, less education and being Black. Those people who had experienced more than one episode of depression were less likely to drop out of treatment.
Warden, Diane ... [et al] - Predictors of attrition during inital (Citalopram) treatment for depression : a STAR*D report American Journal of Psychiatry 2007, 164: 1189-1197