Mechanisms of Change of Positive Interventions in Reducing Vulnerability for Depression

A cross-over design will be used comparing measures before and during both a mindfulness- and a positive fantasizing intervention period in individuals who remitted from two major depressive episodes (i.e. remitted Major Depressive Disorder (rMDD) patients) and a never-depressed control group. After checking for eligibility of the participants, participants will fill-out several questionnaires about their personal characteristics, experiences and expectations. These questionnaires will be used to study individual characteristics that could serve as treatment markers predicting the effectivity of interventions. Furthermore, diary measures of thought patterns (experience sampling method [ESM]), behavioural measures (using the Sustained Attention to Response Task [SART]), actigraphy, (neuro)physiological measures (impedance cardiography [ICG], electrocardiography [ECG] and electroencephalogram [EEG]) and measures of depressive mood (self-report questionnaires) will be performed during the week before (pre-) the interventions and the week during (peri-) performance of the interventions. In-between pre-and peri-intervention measures, there is a one month wash-out period. The order of the interventions will be counterbalanced across participants. Pre- and peri-intervention measures will be compared to study intervention effects in remitted MDD patients, remitted MDD patients vs. healthy controls and in relation with individual characteristics

Inclusion criteria

In order to be eligible to participate in this study, all participants must meet all the following criteria:

• Participants should be between 18 and 60 years old. Participants should not exceed 60 years of age in order to minimize aging-related decline in information processing;
• Participants should display normal intelligence (IQ>85, as assessed with the Dutch Adult Reading Test and/or having finished an education on at least vocational level) in order to assure sufficient task comprehension.

Participants in the remitted Major Depressive Disorder group should meet the following criteria to make sure that participants are at high risk of depressive relapse and currently show no clinically relevant severity of depressive symptoms:

• Remitted participants should have experienced at least two depressive episodes, according to criteria defined by the Diagnostic Statistical Manual, version 5 (DSM-5), experienced in past ten years;
• Remitted participants should score 21 or lower on the Inventory of Depressive Symptomatology (IDS-SR30), indicative of the absence of clinically relevant depressive symptoms.

Exclusion criteria

Furthermore, individuals who meet any of the following criteria will be excluded from participation in this study:

• Fulfilling criteria for any current DSM-5 diagnosis as objectified with the Structured Clinical Interview for DSM-5 (SCID-5);
• Daily use of anti-depressive medication, benzodiazepines, methylphenidate, beta blockers or other medication potentially influencing electrocardiogram currently or in the last four weeks;
• Recent engagement (defined as in their last episode, or as one year prior to inclusion in case the last episode was more than a year before inclusion) in preventive cognitive therapy including the positive fantasizing technique and/or have recent experiences (defined as daily practice in the past two years for at least two weeks) with mindfulness, meditation, or mindful yoga. This criterion prevents underestimation of true effects of mindfulness and/or positive fantasizing and maximizes treatment effects;
• Participation in another clinical intervention study at the moment of inclusion in the study to prevent overlapping intervention effects.

Individuals for the Never-Depressed control group who additionally meet any of the following criteria will be excluded from participation of this study:

• Presence of symptoms of depression according to the IDS-SR30 (score > 13), to make sure participants are not currently experiencing clinically relevant depressive symptoms;
• Any life-time psychopathology of any disorder as objectified with the SCID-5.