Participants

Inclusion criteria were that participants were students or staff at the host university, and this was ensured as the intervention was hosted on the university’s secure virtual learning system which was only accessible to students and staff. No exclusion criteria were applied. Participants were 155 (124 female) students (n = 120) and staff (n = 35) from a university in the South of England who had responded to either a recruitment email or posters that had been placed around the university campus. Age ranged from 18 to 68 years (M = 31.03 years, SD = 11.64 years). Whilst no inclusion or exclusion criteria based on participant’s distress was employed during this study, it is of note that 56% of our sample scored at least one standard deviation over the general population mean on the PHQ-4 measure (cf. Löwe et al. 2010), and 81% scored at least half a standard deviation above a community mean on the perceived stress scale (Cohen and Williamson 1988; cf. Rose et al. 2013). Moreover, more than half of the sample (61%) scored at or above the cut-off for likely caseness of anxiety (31%), depression (6%) or both (24%; Kroenke et al. 2009). The study protocol was approved by the ethics committee at the host university and informed consent was obtained from each participant prior to participation.

Procedure

The study was advertised on the university campus. All participants signed up to the ‘Learning Mindfulness Online’ course, gave informed consent and then completed the baseline questionnaires online, hosted on the Bristol Online Survey platform. A number of studies have now demonstrated that paper-and-pencil and Internet data collection methods are generally equivalent, including measures of perceived stress and symptoms of depression (e.g. Herrero and Meneses 2006). Within 24 h of completing the baseline questionnaires, participants were randomised, by a researcher blind to participant details, using a computer-generated blocked random allocation method (block size 15), to either start the mindfulness psychoeducation intervention immediately (mindfulness psychoeducation condition), to start the mindfulness meditation intervention immediately (mindfulness meditation condition) or to join a wait list control condition. Participants were blind to hypotheses regarding the role of formal mindfulness meditation in this study, and were informed that they would be assigned to “a version of the ‘Learning Mindfulness Online’” or a waiting list condition.

The intervention groups were given instant access to their allocated version of the ‘Learning Mindfulness Online’ course and were encouraged to log-on to become familiar with their site. Those assigned to the waiting list condition were informed that they would be invited to join the ‘Learning Mindfulness Online’ course 1 month later.

The Online Mindfulness-Based Interventions

The ‘Learning Mindfulness Online’ interventions were delivered using the university’s virtual learning facility, built with an open source learning management system, Moodle. Materials included a streaming video, embedded text and an article to be downloaded and read with a pdf reader. This virtual learning facility is accessible via a university login on any web-enabled device on or off campus. Both interventions included identical information about mindfulness, advice on applying the principles of mindfulness to activities of daily living (informal practice), an invitation to record mindful activities, a journal to reflect on experiences of mindfulness, study information, help and assistance (study information sheet, contact email for researchers, university counselling services and mental health charities).

Information about mindfulness was presented in a brief video (5 min), embedded text (900 words) and a downloadable pdf (2000 words) each of which describe mindfulness as paying attention in the present moment, with openness and curiosity, instead of judgement. This included the idea of bringing attention to our bodily sensations, thoughts and feelings as well as to present moment external events. Guidance on applying mindfulness to daily life is also included (850 words); this recommends choosing one routine activity per day in week 1 (brushing your teeth, drinking tea, coffee or juice, loading the washing machine, etc.) and offers a daily guided walking exercise for week 2 of the intervention. The ‘formal practice’ intervention also included information about mindfulness meditation practice and audio practices that users were invited to follow daily. Participants were given access to the intervention for a period of 14 days; all elements of their assigned interventions were available from the beginning. The researcher teams’ email address provided was for technical difficulties only, beyond that the programme was self-guided, without personal contact.

In the formal practice intervention, participants were invited to listen daily to a 10-min audio track that contained a guided, mindfulness sitting meditation. The meditation practice was adapted from Person-Based Cognitive Therapy (Chadwick 2006) and MBCT (Segal et al. 2013) and is one that has been used in three previous published studies (Chadwick et al. 2016; Dannahy et al. 2011; Strauss et al. 2012). The mindfulness practice was associated with significant improvements in self-reported mindfulness in an RCT for intervention participants relative to those in the control condition (Strauss et al. 2012), and a qualitative study including this mindfulness practice generated themes similar to themes reported in MBIs with more prolonged mindfulness practices (Strauss et al. 2015). Two versions of the10-min meditation were provided, so the participants could choose to listen to a female or male voice, as they preferred. Both versions were recorded by experienced clinical psychologists who were also accredited MBCT practitioners. The audio recording invites participants to adopt a comfortable, upright sitting position and guides participants to bring non-judgemental attention first to the body (from the feet to the head), then the breath and finally to thoughts and feelings.

Participants in both conditions also received standardised reminder emails at 3-day intervals, with four reminder emails being sent in total. Each reminder email invited participants to continue with the intervention, and contained ‘hints and tips’ for their mindfulness practice. In week one, these consisted of general mindfulness practice information, e.g. ‘there is no right or wrong way to practice mindfulness’. In the second week, they provided suggestions on ways in which mindfulness could be brought into participants’ everyday life, e.g. mindful eating, mindful walking.

The standardised emails were sent every 3 to 4 days and, after 2 weeks, all participants received a standardised email with a direct link to the end of study questionnaire. Participants received three reminder emails in total for the closing questionnaire. Those who completed the closing questionnaire received a final email thanking them for their participation. All waiting list participants were then enrolled onto the ‘Learning Mindfulness Online’ course and given access to the full learning mindfulness online programme.

Measures

Five Facet Mindfulness Questionnaire (FFMQ; Baer et al. 2006)

This 39-item self-report scale is used to measure changes in participant’s tendency to be mindful in daily life. Participants are asked to what extent each of the statements are true of them. Each item is on a five-point Likert-type scale from 1—never or very rarely true to 5—very often or always true. We report on a composite measure including four of the original five FFMQ subscales (excluding ‘observe’). Psychometric papers on the FFMQ have supported the use of a total scale score (omitting scores from the observe subscale) in addition to subscale scores (e.g., Baer et al. 2008; Gu et al. 2016; Williams et al. 2014b).The FFMQ scale reported showed good internal consistency at baseline in this sample, Cronbach’s alpha = 0.93.

Perceived Stress Scale (PSS; Cohen and Williamson 1988)

The 10-item Perceived Stress Scale (PSS) is designed to measure how unpredictable, overloaded or uncontrollable participants have found their lives. The scale asks participants to rate how often they have felt or thought they had been out of control, overloaded and unpredictable during the last 2 weeks on a five-point Likert-type scale from 0—never to 4—very often. The PSS showed good internal consistency at baseline in this sample, Cronbach’s alpha = 0.89.

Patient Health Questionnaire for Depression and Anxiety (PHQ-4)

The PHQ-4 is a brief screening measure for anxiety and depression, focusing on experiences during the previous 2 weeks (Kroenke et al. 2009). Four items are answered on a four-point Likert scale ranging from 0—not at all, to 3—nearly every day, an example item being: “Over the past two weeks have you been feeling down, depressed, or hopeless?” Total score is determined by adding together the scores for each of the four items. Scores are rated as normal (0–2), mild (3–5), moderate (6–8) and severe (9–12). The PHQ-4 showed good internal consistency at baseline in this sample, Cronbach’s alpha = 0.84.

Perseverative Thinking Questionnaire (PTQ; Ehring et al. 2011)

The PTQ measures dysfunctional repetitive negative thinking as a transdiagnostic process, independent of disorder-specific thought content. Respondents characterise their typical responses to negative experiences by rating 15 statements, such as “I feel driven to continue dwelling on the same issue” on a five-point Likert scale (0—never to 4—almost always). Confirmatory factor analysis suggests a single higher-order factor and three lower-order factors (Ehring et al. 2011). Only the total score was used in our analysis. This decision was supported by exploratory factor and correlational analyses conducted on the baseline scores, which unambiguously yielded a single factor and high correlations between the proposed subscales (Pearson’s r 0.76 to 0.82). The PTQ showed good internal consistency at baseline in this sample Cronbach’s alpha = 0.96.

Engagement and Experience Questionnaire

At baseline, participants indicated their previous meditation experience using a five-point Likert scale (“How much experience of meditation do you have?”, 1 = none to 5 = 5+ years). After the 2-week intervention period, they were asked to indicate how often they had practiced mindfulness meditation (“How often have you practiced mindfulness meditation over the last two weeks?”) and how often they had applied the principles of mindfulness to activities of daily living during the 2-week intervention, (“How often have you applied the principles of mindfulness to your activities during the last two weeks?” 1 = not at all to 5 = at least once a day), how frequently they intended to continue to practice (“How frequently do you intend to continue practicing mindfulness?”, 1 = not at all to 5 = at least once a day) and how frequently they had read intervention related emails (“Did you read the reminder emails from the mindfulness research group?”, 1 = never to 5 = always). In order to assess participants’ experience of the mindfulness online intervention, they were asked how beneficial they thought the 2-week intervention had been for them (“Do you think practicing mindfulness during the past 2 weeks was beneficial for you?”, 1 = not at all to 5 = very beneficial).

Data Analyses

For tests of intervention effectiveness, missing data were replaced using the baseline-observation carried forward (BOCF) method (Gupta 2011). These analyses therefore included all participants who entered the study irrespective of completion of post-intervention questionnaires. BOCF makes the assumption that intervention participants who fail to complete post-intervention measures did not benefit and therefore is a conservative method of taking account of missing data. This method is therefore likely to underestimate the true effect of an intervention (Liu-Seifert et al. 2010). Completer analyses are also reported.

To determine the effects of intervention condition on mindfulness, stress, perseverative thinking and symptoms, the primary analyses performed using IBM SPSS version 24 were 3-way (group) analyses of covariance (ANCOVA) on pre-post change in FFMQ, PSS, PHQ-4 and PTQ scores, including baseline measures of PHQ-4 and PTQ as covariates to control for baseline differences between groups on these measures. Significant main effects were explored using Helmert contrasts to compare the intervention groups to each other, and the mean of both intervention conditions to the wait list control. Simple contrasts (to look at change over time within each condition), their effect sizes (d) and 95% confidence intervals (CIs) were calculated using Eqs. 4, 15 and 18 in Nakagawa and Cuthill (2007).

As recommended (Kazdin 2007), only complete data sets were used for the mediation analyses. Mediation analysis was conducted on completer sample data to test the hypothesis that improvements in perseverative thinking would mediate the relationship between condition and improvements in stress, anxiety and depression. Bootstrapped 95% bias-corrected confidence intervals were calculated with 5000 resamples using MPlus (demo version 7.2), a syntax-driven programme for estimating a wide range of structural equation models, including mediation models (Muthén and Muthén 1998–2012). This approach was used instead of the causal steps approach (Baron and Kenny 1986) as it is both more powerful and more robust to violations of assumptions of multiple regression analysis (Preacher and Hayes 2008). This provides the 95% confidence intervals of the indirect effect of the intervention group on improvements in stress and anxiety/depression through the proposed mediator (improvements in perseverative thinking). This effect is deemed significant if the 95% confidence intervals do not cross zero. Non-bootstrapped path coefficients were also calculated for the effect of the intervention group on the mediator (path a), the effect of the mediator on the dependent variable whilst controlling for the independent variable (path b) and the effect of the intervention group on the dependent variable whilst controlling for the mediator (path c’; see Fig. 1). As the independent variable, condition, is multicategorical but not dichotomous (with three levels: mindfulness meditation, mindfulness psychoeducation and wait list control), we used Hayes and Preacher’s (2014) MPlus code to implement their recommended method of mediation analysis with a multicategorical independent variable. This estimated a single model for each dependent variable (perceived stress and anxiety/depression symptom severity). In both models, the mindfulness meditation condition was used as the reference category; the contrasts were mindfulness meditation versus mindfulness psychoeducation, and mindfulness meditation versus wait list control.