Major depressive disorder is often a chronic disorder, and treatments need to reduce symptoms over long periods of time. There is evidence that an acute course of psychotherapy may lengthen the period of time before relapse or recurrence (Biesheuvel-Leliefeld, 2015; Steinert, 2014). In addition to this, Cuijpers, 2013 and Dobson, 2008 found acute phase-only cognitive behavioral therapy (CBT) without maintaining patients on antidepressants to be equal in efficacy to maintaining patients on antidepressants for 6-18 months after remission (Cuijpers, 2013; Dobson, 2008).

It appears that antidepressants may have a significantly higher effect size in patients with severe depression (Fournier, 2010). In addition to this, there is some evidence that patients with mild depression may preferentially respond to psychotherapy, while patients with moderate to severe depression may preferentially respond to antidepressants (Spielmans, 2011).

Segal, 2010 and Kuyken, 2015 found patients given psychotherapy and withdrawn off of antidepressants to have comparable rates of relapse to those remaining on maintenance antidepressant treatment for up to 24 months (Kuyken, 2015; Segal, 2010).

Generally, antidepressants and psychotherapy appear to be equally effective in the acute treatment of depression (Spielmans, 2011) and the selection of the treatment modality may be affected by patient preference, treatment availability and relative cost.

Persistent Depressive Disorder

The majority of the literature on persistent depressive disorder is based on DSM-IV criteria and divides it into the following categories:

1. Pure dysthymia for the whole duration
2. Major depression that is chronic for at least two years
3. Eecurrent major depression without inter-episode recovery
4. Major depression that is superimposed on a pre-existing dysthymic disorder (persistence for at least two years defines this category)

DSM-5 consolidated DSM-IV and included dysthymic disorder and chronic major depressive disorder into one large category called persistent depressive disorder. DSM-5 details four subsets of persistent depressive disorder, which are a slight variation of the above.

However, for treatment purposes, the subsets of chronic depressive disorders/persistent depressive disorder can be placed into two main categories – pure dysthymia and chronic disorders involving major depression. Available literature indicates that pure dysthymia responds differently to treatment than the three other subsets of chronic depressive disorders involving major depression.