The goal of psychological and behavioral intervention is to help people live better lives. It is possible, however, that such interventions can also cause harm for select individuals. This is as true of mindfulness meditation as it is of other cognitive-behavioral and therapeutic interventions. Researchers want to learn who might be most vulnerable to adverse effects and under what circumstances. Examples of adverse effects include anxiety, depression, flashbacks, psychotic symptoms, and alterations in identity. 

There is anecdotal evidence that adverse effects may be more common in intensive meditation retreats than in standard mindfulness-based interventions (MBIs). Aizik-Reebs et. Al [Behaviour Research and Therapy] used experience sampling (checking in on how participants felt at random moments) to evaluate the frequency of momentary and persistent adverse effects associated with participation in a MBI. 

The researchers recruited 82 meditation-naïve Israelis (52% female; average age = 25 years) seeking stress-reduction. Prior to starting the MBI, participants were assessed on measures of mindfulness, anxiety, depression, worry, rumination, and distress tolerance.

The 21-day MBI included 3 group-based session held once per week for 90 minutes each, and 3 web-based 30-minute individual sessions. Session content included focused-attention, open monitoring, and movement meditations with encouragement for daily home practice. 

Participant experience sampling was conducted several times a day over a 28-day period beginning 3.5 days before and ending 3.5 days after the MBI. During sampling, participants rated the extent of their negative emotions and cognitions. Experience samples were taken immediately after three mindfulness meditation sessions, and at random times throughout the day.

Momentary adverse effects were defined as significant (>1.96 standard deviations) deteriorations in mood during meditation compared to participant mood during normal daily activities. Sustained adverse effects were defined as significant deteriorations in mood during the 3.5 days after the MBI relative to the 3.5 days prior to the MBI.

The results showed 87% of participants experienced at least one momentary adverse effect during the three sampled meditation sessions, with 42% having them during two and 28% in all three sessions. The most common adverse events were momentary increases in anxiety (70% of adverse events), rumination (29%), sadness (22%), and depressed mood (17%).

Twenty-five percent of the participants showed a sustained adverse effect (poorer mood after the MBI than before). The most common sustained adverse effects were increases in worry (9%), decreases in happiness (7%), and increases in rumination (6%). Momentary adverse effects and measures of pre-intervention emotional vulnerability were uncorrelated with sustained adverse effects. 

The study shows moments of anxiety, worry, and negative mood are commonplace in novice meditators during early stages of a meditation program, but these momentary experiences are not predictive of sustained adverse effects. About a quarter of meditation-naïve participants experienced poorer mood after completing the MBI program than before.

It is possible that increases in negative mood are due to facing previously avoided problems, transitioning to new coping strategies, increased awareness of feelings, or a genuine deterioration in functioning. The study is limited by a brief follow-up period and the absence of a control group.

Reference:

Aizik-Reebs, A., Shoham, A., & Bernstein, A. (2021). First, do no harm: An intensive experience sampling study of adverse effects to mindfulness training. Behaviour Research and Therapy.

Link to study