Objectives Face-to-face mindfulness interventions have been shown to significantly decrease perceived stress, anxiety and depression and research is beginning to show similar benefits for such courses delivered via the internet. We investigated the feasibility and effectiveness of an online mindfulness course for perceived stress, anxiety and depression.

Design A follow-up investigation of an online mindfulness course. Previous research examining the change in perceived stress showed promising results. Measures of anxiety and depression were added to the online mindfulness course and these were investigated as well as perceived stress using a new, larger sample.

Participants Participants (N=273) were self-referrals to the online course who completed the outcome measure immediately before the course, upon course completion and at 1 month follow-up.

Intervention The programme consists of 10 sessions, guided meditation videos and automated emails, with elements of Mindfulness-Based Stress Reduction and Mindfulness-Based Cognitive Therapy, completed at a pace to suit the individual (minimum length 4 weeks).

Primary and secondary outcome measures The Perceived Stress Scale, the Generalised Anxiety Disorder Assessment-7 and the Patient Health Questionnaire-9 (for depression). Mindfulness practice was self-reported at automated time points upon login, once the exercises and sessions for each week were completed.

Results Perceived stress, anxiety and depression significantly decreased at course completion and further decreased at 1 month follow-up, with effect sizes comparable to those found with face-to-face and other online mindfulness courses and to other types of intervention, such as cognitive behavioural therapy for stress. The amount of meditation practice reported did affect outcome when controlling for baseline severity.

Conclusions The online mindfulness course appears to be an acceptable, accessible intervention which reduces stress, anxiety and depression. However, there is no control comparison and future research is required to assess the effects of the course for different samples.