Frequency and change mechanisms of psychotherapy for depression.

Background of the study:

Recently, a strong association was found between the number of psychotherapy sessions per week and treatment outcome. However, there is no clarity about the optimal session frequency neither about the change mechanisms in the effects of psychotherapy. Finding an effect for session frequency will lead to higher therapy efficacy and lower the economic burden for depression while understanding the processes that account for therapeutic change might make us better able to optimize treatments.

Objective of the study:


The effectiveness of psychotherapy can be improved by increasing the frequency of sessions at the beginning of therapy. In addition, understanding processes that account for therapeutic change might enable us to optimize treatments.

Study design:

Multicenter randomized trial with four parallel groups (n=230) : a) twice-weekly sessions at the start of CT, b) twice-weekly sessions at the start of IPT, c) once-weekly sessions at the start of CT, d) once-weekly sessions at the start of IPT. Randomization (patient level) will be pre-stratified according to severity (high severity = BDI score =>30; low severity = BDI score <=29).

Study population:

230 depressed patients with a major depressive disorder (MDD) aged 18-65 years seeking treatment recruited from several Dutch mental health centers.

Intervention:

Twice-weekly sessions of cognitive therapy or interpersonal therapy at the start of therapy, up to 20 sessions in total. Standard intervention to be compared to: once-weekly sessions of cognitive therapy or interpersonal therapy at the start of therapy, up to 20 sessions in total.

Nature and extent of the burden and risks associated with participation, benefit and group relatedness:

Patients will be invited to a clinical screening interview. Other measurements will be administered online, which guarantees maximum flexibility for the participant. Participation to the venipuncture will be an optional part of the study. Though the burden includes a time investment of the patient, no risks are associated with participation in the study.

We expect that twice-weekly sessions will be more cost-effective and lead to better treatment outcomes than once-weekly sessions at the start of psychotherapy. Furthermore, learning processes, therapeutic-specific variables and physiological factors are expected to be involved as mechanisms of change in the effects of psychotherapy.

T0=baseline; T1-T6= month 1-6; T9= month 9; T12= month 12; T24=month 24

Cognitive therapy includes psycho-education (explanation of the treatment rationale and the general procedures in CBT treatment), behavioral activation (motivating the patient to build a day structure and increase activities), cognitive therapy (examining automatic negative thoughts and dysfunctional assumptions) and relapse prevention (identifying and adopting techniques/strategies to prevent depressive symptoms to re-occur).



Interpersonal therapy consists of three phases. The initial phase includes an evaluation of symptoms and interpersonal relations, making a case formulation and the agreement on a treatment plan. During the second phase the patient and therapist focus on working on the interpersonal problem with the expected result of reducing symptoms. The final phase compromises discussion of ending treatment, reviewing improvement, establishing gains and anticipating future problems.



CT and IPT differ in terms of target (cognitions and behavior vs. interpersonal functioning), approach (directive vs. empathic-reflective) and method (homework assignment vs. no assignments) .