Online Mindfulness-Based Cognitive Therapy in Depressed Sample

The goal of this clinical trial is to evaluate the effectiveness of the online 6-weeks Mindfulness-Based Cognitive Therapy (iMBCT) in depressed sample and compare the guided intervention to an unguided one. The main questions the study aims to answer are:

* To what extent completing iMBCT will reduce the severity of depressive symptoms in mild to moderately depressed sample?
* What are the differences in participants who completed the program or responded to treatment and those who discontinued it?
* What are the differences in treatment effect between two active conditions (guided and unguided iMBCT) and a passive one - waiting-list group?

Researchers will compare two iMBCT interventions with a waiting-list group to assess the therapeutic effects of iMBCT on depression, anxiety and other measures related to the mental health.

Depression affects more than 300 millions of people worldwide and is perceived as a largest contributor to global disability (World Health Organisation, 2017). Although the research into depression has been expanding in the last decades (Ledford, 2014), the epidemiological data suggests that a prevalence trend is not decreasing (Ormel, Cuijpers, Jorm et al., 2020).

Standard treatment such as psychotherapy or pharmacotherapy is expensive and often associated with other barriers such as limited availability of specialists or waiting-lists (Biringer, Sundfør, Davidson, 2015), which stresses the importance of seeking and investigating other approaches that could address mentioned issues (Rudd \& Beidas, 2020).

With the development of technology, online psychological interventions have been created to offer more accessible help. Among the various programs aimed at reduction of psychological distress, the ones based on cultivating mindfulness, are exponentially increasing in popularity (Lee, Kim, Webster et al., 2021).

One of the few most examined MBI's protocols, considered as "gold-standard" (Van Dam et al., 2018) is Mindfulness-Based Cognitive Therapy (MBCT, Teasdale, Segal, Williams, 2000). Recent meta-analysis has shown that the intervention could treat current episodes of depression (Goldberg, Tucker, Greene et al., 2019). In the latest National Institute for Clinical Excellence (2022) guidelines MBCT was listed as one of the first-choices for less severe depression.

Several studies demonstrated the effectiveness of the online version of MBCT (iMBCT) in treating depressive symptoms (Segal, Dimidjian, Boggs et al., 2020; Ritvo, Knyahnytska, Wang et al., 2021; Nissen, Zachariae, O'Connor et al., 2021), however the field is still fairly new and more research is needed to comprehensively evaluate the clinical utility of the intervention.

In this study the investigators decided to evaluate the effectiveness of two conditions of 6-weeks iMBCT (guided and unguided) and compare those two with a waiting-list group.

Individuals willing to take part in the study will complete an online screening test. Participants meeting the initical criterions - mild to moderate depressive symptoms - will be asked to take part in a structured clinical interview to increase the validity of the assessment and exclude those with comorbid psychiatric disorders.

Then after recruitment, participants will be randomized to one of the three mentioned above conditions. The unguided intervention will consist of the same thematic modules as guided one, however instead of online meetings materials will be uploaded on the platform.

Despite pre-test and post-test after six weeks, there will be follow-up measure after 3 months. Another outcome measure will be ecological momentary assessments taking place during the intervention.

Eligibility Criteria:
Inclusion Criteria:

* meeting the screening criterions for depression
* confirmed diagnosis in the clinical interview - mild to moderate depressive episode
* 18 years old or older
* informed consent
* fluent in Polish
* willing to be randomized to intervention or waiting list group

Exclusion Criteria:

* lack of depressive symptoms constituting mild or moderate episode of depression
* suicidality
* severe depression
* current substance use disorder, psychotic disorders, bipolar
* current psychotherapy
* if antidepressant medication: has not been stable over the last 4 weeks