It turns out that there are a fair number of studies of CT and related approaches for relapse prevention with recurrent unipolar depression as well as a fair amount of debate. The good news is that CT, Mindfulness-Based CT, and CT designed for relapse prevention each significantly reduce the relapse rate. In fact, it appears that they cut the relapse rate roughly in half.

The bad news is that, despite this, there still is a significant relapse rate (perhaps 35-45%) among people with recurrent depression who've had CT. This is not bad at all compared with a 70-90% relapse rate for clients treated with antidepressants alone. However, we don't have a reliable way to predict who's going to relapse and it is not yet clear whether the relapse-prevention effect of CT fades over time or not.

This presents a problem for the clinician and client. Does the patient need to stay on medication preventively once they've overcome their depression or not?

This is not an easy question to answer. We can find out if they need to stay on medication in order to maintain their improvement simply by tapering off the medication (with their psychiatrist's consent) and monitoring their mood. If their depression returns and persists despite our efforts, we have discovered that the client needs to remain on medication in order to maintain their improvement. If their depression does not return, we have discovered that they do not need medication at the moment but we do not know if remaining on medication will help prevent relapse.

Some clients prefer to "play it safe" by remaining on medication in the hopes that it will reduce the risk of relapse. Others prefer to take medication only if it is clearly necessary and want to see how they do without medication. Both approaches seem reasonable and my current approach is to discuss the pros and cons of remaining on medication with the client and have them also discuss this issue with their psychiatrist before deciding what to do. We also explicitly discuss what they need to do in order to maintain their gains, identify high-risk situations and plan how to cope with them, and identify early warning signs of impending depression.

It appears that, after successfully completing CT, a majority of clients with recurrent depression can go for several years without relapsing but that a significant minority will relapse within a few years. It is clear that clients who receive CT alone have a lower relapse rate than those who receive medication alone. It is not clear if remaining on medication significantly reduces the relapse rate for clients who have received combined treatment (most of the studies have compared CT with meds without looking at combined treatment).

One approach to preventing relapse with recurrent depression is to use maintenance CT (i.e. to continue meeting with the client periodically to monitor mood, to address any problems that arise, and to intervene promptly if depression reoccurs. The one study I found on maintenance CT (Blackburn & Moore, British Journal of Psychiatry, 1997, 328-334) found that it worked at least as well as maintenance antidepressants.