Couples were treated for 12 - 20 sessions of psychotherapy or 1 year of antidepressant (desipramine) treatment. In a comparison between the pharmacological intervention and CBT manualized treatment for couples, researchers found that pharmacotherapy had a 50 percent drop-out rate, whereas couples therapy had only a 15 percent dropout rate. Both groups show a lessening of depression after a year, however, couples in CBT treatment showed significantly more improvement-- a difference that was maintained after 1 year follow-up.

The London Depression Intervention Trial: Randomised controlled trial of antidepressants v. couple therapy in the treatment and maintenance of people with depression living with a partner: Clinical outcome and costs.
By Leff, Julian; Vearnals, Simon; Brewin, Chris R.; Wolff, Geoffrey; Alexander, Barbara; Asen, Eia; Dayson, David; Jones, Elsa; Chisholm, Daniel; Everitt, Brian
British Journal of Psychiatry. 2000 Aug Vol 177 95-100