Historically, research into meditation has tended to emphasise beneficial outcomes rather than the processes involved or potential adverse effects. However, there is a growing body of evidence that suggests there may be risks associated with meditation practice, in both clinical and non-clinical settings. Close examination of the scientific literature reveals that even in early meditation research, adverse effects were identified in therapeutic contexts. Notably, renowned psychologists Arnold Lazarus (1932 – 2013) and Albert Ellis (1913 – 2007), co-founders of Cognitive Behaviour Therapy (CBT), both expressed concerns regarding negative side effects associated with therapeutic meditation. For example, in 1976 Lazarus reported that some of his patients had severe disturbances after practicing TM, including depression and suicidal ideation, leading in one case to a serious suicide attempt. He wrote:
[meditation] is not a panacea. In fact, when used indiscriminately, there are clinical indications that the procedure can precipitate serious psychiatric problems such as depression, agitation, and even schizophrenic decompensation.
Lazarus was also one of the first researchers to argue that individual differences should be taken into account when deciding whether meditation is an appropriate intervention, noting:
Scientific psychology has emphasized the significance of individual differences. Folklore is equally aware that “one man’s meat is another man’s poison.” Yet popular systems and movements from psychoanalysis to Transcendental Meditation (TM) generalize and universalize, present their views and findings in absolutistic rather than probabilistic terms, and depart from established scientific pathways in several other respects. Their procrustean deftness at fitting everyone to their system damages the integrity and individuality of persons who are temperamentally and otherwise unsuited to their procedures.
In 1984, Ellis also expressed concerns regarding the therapeutic use of meditation, arguing that it had the potential to be more harmful than many other psychological techniques because of its association with spirituality and religion. Specifically, he argued that the traditional spiritual goals associated with meditation (such as transcendence or the experience of a higher consciousness) were probably “illusory” and “highly disturbed,” since no human was likely to achieve them. Therefore, he conceded, meditation combined with mysticism “includes highly dangerous, anti-therapeutic elements.” However, Ellis was broadly supportive of the use of secular meditation in therapy, but like Lazarus, argued that the practice could be harmful for certain groups of individuals, particularly those with obsessive-compulsive and ruminative tendencies, noting: “A few of my own clients have gone into dissociative semi-trance states and upset themselves considerably by meditating.” Interestingly, Ellis argued that the greatest potential danger of meditation was that it was “a highly palliative procedure;” that is, a diversionary technique that helped people to feel better temporarily, but that ultimately distracted them from developing the necessary skills required to make significant positive change in their lives.
A more severe example of the potential adverse effects of meditation was reported in a 1975 case study by Alfred French and colleagues. The authors describe the case of a 39 year old woman who, several weeks after starting TM practice, experienced altered reality testing and behaviour. While the patient had no pre-existing clinical issues, after starting meditation she experienced euphoric fantasies with mystical elements, dysphoric moods and unusual behaviour that resembled psychosis. The authors argued that the continued presence of an altered state of consciousness (which began within days of starting TM), and the occurrence of “waking fantasies” (which began shortly after), suggested a causal relationship between meditation and the subsequent psychosis-like experience, and cautioned that “this form of meditation carries the risk of psychosis-like and potentially dangerous regression.” However, the authors also emphasised that the psychosis-like symptoms appeared to be the result of a specific meditation-induced phenomenon, and were distinct from standard clinical definitions of psychosis, writing: “such ‘trips,’ while often clinically psychosis-like, are distinct clinical entities from functional psychoses.”
Another study of TM by Leon Otis noted that adverse effects such as pervasive anxiety and depression occurred in a significant percentage of people who practiced TM (slightly less than half of the 1,900 subjects), and that the probability of such effects occurring was higher among psychiatric populations. Of particular interest is Otis’s finding that more adverse effects occurred among long-term meditators and TM teacher trainees than among novice meditators. He writes:
These data suggest that the longer a person stays in TM and the more committed a person becomes to TM as a way of life (as indicated by the teacher trainee group), the greater the likelihood that he or she will experience adverse effects. This contrasts sharply with the promotional statements promulgated widely by the SIMS (Students International Meditation Society), IMS (International Meditation Society), WPEC (World Plan Executive Council), and related TM organisations that TM is a simple, innocuous procedure.
Additionally, Otis noted that some participants in his study continued to practice meditation despite experiencing adverse effects, and had “compared meditation to a drug addiction … not wishing to continue but unable to stop.”
Dissociative symptoms have also been reported as a result of meditation practice. Arthur Deikman reported cases in which depersonalisation and derealisation occurred in individuals practising an experimental procedure based on classical descriptions of contemplative meditation. Raymond Kennedy also reported two meditation-related cases in which patients experienced depersonalisation and derealisation, including out-of-body experiences, and required psychiatric treatment. Additionally, Richard Castillo conducted interviews with six TM meditators and concluded that meditation can cause both depersonalisation and derealisation, and that the depersonalised state can become an apparently permanent mode of functioning.
Adverse effects have also been found among meditation retreat participants. For example, Deane Shapiro conducted a study on a non-clinical population (n = 27) at a vipassana meditation retreat and found that 62.9% of participants experienced at least one adverse psychological effect from meditation, including feelings of anxiety, panic, depression, confusion and disorientation. Two participants (7% of the sample studied) experienced symptoms so severe that they stopped meditating; one participant said the retreat left him “totally disoriented … confused, spaced out,” while the other participant reported “lots of depression, confusion … severe shaking and energy releasing.” Shapiro also found a trend that, while not statistically significant, lent support to Otis’s earlier finding that meditators who had practiced the longest (in this case, over 8.5 years) reported the highest frequency of adverse effects.
More recently, Tim Lomas and colleagues conducted a study on the effects of secular meditation (including mindfulness techniques) in a non-clinical population (n = 30) and found that while meditation was portrayed overall as a beneficial activity, all participants found it challenging at least some of the time. Additionally, one quarter of participants in the study encountered “substantial difficulties” with meditation, including troubling experiences of self, troubling thoughts and feelings which were hard to manage, the exacerbation of mental health issues such as depression and anxiety, and in two cases, psychosis requiring hospitalisation.
Several recent studies have also looked at the re-experiencing of trauma as a potential adverse effect of meditation. Specifically, there has been recognition that meditation might cause emotional flooding or re-traumatisation in certain individuals. Jane Compson argues that in particular, intensive, silent meditation retreats may leave meditators at risk for traumatic activation, which manifests as panic, anxiety, rage and insomnia. In his book Trauma-Sensitive Mindfulness David Treleaven argues that mindfulness meditation, practiced without an awareness of trauma, can exacerbate symptoms of traumatic stress, leading to flashbacks, dissociation and retraumatisation. Treleaven also describes a specific meditation-induced phenomenon he terms “contemplative dissociation,” which he defines as “a disconnection between thoughts, emotions and physical sensations that is exacerbated by contemplative practice.”
In a comprehensive review of meditation adverse effects, M. Kathleen Lustyk and colleagues consulted seventeen primary publications and five secondary reports and literature reviews, including several of the studies mentioned above. The authors found that the most frequently reported meditation adverse effects were mental health issues, with the more serious cases including severe affective and anxiety disorders (for example, mania and PTSD), temporary dissociative states, and psychosis. They also reported meditation-related adverse effects on physical health, including increased epileptogenesis (risk of seizures), somatic discomfort arising from holding a meditation postural position, and potential problems associated with loss of appetite, reduced food intake, and difficulty sleeping. The authors also referenced studies in which adverse spiritual health effects were reported, most notably, cases of religious delusions.
It is unclear whether the effects of meditation practices alone can be compared directly with meditation practices in the context of mindfulness-based interventions (MBIs). There are very few reports of adverse effects in MBIs, however some studies do exist. For example, Leigh Burrows conducted a study examining the mindfulness meditation experiences of community college students (n = 13) and found that the majority of students reported negative experiences including increased heart rate, depersonalisation, disorientation, disconnection, self-other boundary dissolution, a loss of spontaneity, a loss of sense of self, and emotional flooding. Burrows noted:
Results from this small qualitative study showed 12 of the 13 participants who chose to participate reported a range of unusual perceptions, sensations, and altered states and experiences of self as a result of mindfulness meditation. Only one participant reported unambiguously positive effects such as increased relaxation, focused attention, productivity, and reduction in stress and worry.
Other recent studies of mindfulness meditation have reported increases in perceived stress and depression, feelings of exhaustion or disorientation, increased false memory susceptibility, and links to criminal thinking.
In one of the most comprehensive studies of meditation phenomena to date, Jared Lindahl and colleagues investigated meditation-related experiences that are normally underreported, “particularly experiences that are described as challenging, difficult, distressing, functionally impairing, and/or requiring additional support.” The authors employed a mixed-methods approach that included qualitative interviews with Western Buddhist meditation practitioners and experts from the Theravada, Zen, and Tibetan traditions. From this study the authors were able to delineate 59 meditation-related experiences across 7 domains: cognitive, perceptual, affective, somatic, conative, sense of self, and social. Whether a meditation-related experience was interpreted by the experiencer as adverse depended on a number of influencing factors related to the meditation practitioner, their practice, relationships and health behaviours.
Finally, neuroscientist and meditation adverse effects expert Willoughby Britton has reported that in addition to the above research studies, there exist numerous anecdotal reports of meditators in both clinical and non-clinical populations experiencing psychological and physical disturbances that appear to be directly related to meditation. Some of these instances were severe enough to require medication and hospitalisation and many were serious enough to have become a clinical problem that lasted, on average, for more than three years.
Should we be excessively worried about this? No. Should we be aware of this? Absolutely.
Severe adverse effects from meditation are a relatively rare occurrence, however they do occur and this cannot be denied. Additionally, meditation is a practice that is designed to “shake up” our sense of our selves and our world, and this presents its own unique challenges. Hence, meditation teachers and practitioners need to be aware of potential difficulties that may occur (both the normal “growing pains” of contemplative development and the rarer adverse effects) and be fully equipped to deal with anything that does arise.
 A. Lazarus “Psychiatric Problems Precipitated by Transcendental Meditation,” Psychological Reports 39 (1976): 601-602.
 Lazarus, “Psychiatric Problems,” 601.
 A. Ellis, “The Place of Meditation in Cognitive-behaviour Therapy and Rational-emotive Therapy,” in Meditation: Classic and Contemporary Perspectives, eds. D.H. Shapiro and R. N. Walsh (New York, NY: Aldine Transaction, 2009 ), 692.
 Ellis, “The Place of Meditation,” 672.
 Ellis, “The Place of Meditation,” 672.
 Ellis, “The Place of Meditation,” 672.
 A.P. French, A.C. Schmid, and E. Ingalls, “Transcendental Meditation, Altered Reality Testing, and Behavioral Change: A Case Report,” The Journal of Nervous and Mental Disease 161, no. 1 (1975): 55-58.
 French et al., “Transcendental Meditation,” 55-58.
 French et al., “Transcendental Meditation,” 55-58.
 L. S. Otis, “Adverse Effects of Transcendental Meditation,” in Meditation: Classic and Contemporary Perspectives, eds. D.H. Shapiro and R. N. Walsh (New York, NY: Aldine Transaction, 2009 ),
 Otis, “Adverse Effects,” 204.
 Otis, “Adverse Effects,” 207.
 A.J. Deikman, “Experimental Meditation,” Journal of Nervous and Mental Disease 136 (1963): 329-343.
And A.J. Deikman, “Implications of Experimentally Induced Contemplative Meditation,” Journal of Nervous and Mental Disease 142 (1966): 101-116.
 The terms ‘depersonalisation’ and ‘derealisation’ are distinguished from what Buddhists call ‘non-self.’ In psychiatry, depersonalisation/derealisation disorder (DP/DR) is considered a dissociative disorder and is characterised by disruption or discontinuity in the normal integration of consciousness. DP/DR can potentially disrupt every area of psychological functioning. In Buddhism, ‘non-self’ is generally viewed as a desirable state or trait. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (Washington, DC: American Psychiatric Publishing, 2013), 291.
 R. B. Kennedy, “Self-induced Depersonalisation Syndrome,” American Journal of Psychiatry 133, no. 11 (1976): 1326-1328.
 R. J. Castillo, “Depersonalization and Meditation,” Psychiatry 53 (1990): 158-168. However the author noted that this permanent mode of depersonalisation can occur without there being any significant anxiety or impairment in social or occupational functioning – the meanings the meditator attributes to the experience will determine to a great extent whether anxiety is part of the experience.
 D. Shapiro, “Adverse Effects of Meditation: A Preliminary Investigation of Long-term Meditators,” International Journal of Psychosomatics 39 (1992): 62-67.
 Shapiro, “Adverse Effects,” 64.
 T. Lomas, T. Cartwright, T. Edginton and D. Ridge, “A Qualitative Analysis of Experiential Challenges Associated with Meditation Practice,” Mindfulness 6, no. 4 (2015): 848-860.
 Lomas et al., “A Qualitative Analysis,” 848-860.
 W.B. Britton and A. Sydnor, “Neurobiological Models of Meditation: Implications for Training Young People,” in Teaching Mindfulness Skills to Kids and Teens, eds. C. Willard and A. Salzmann (New York, NY: Guilford Press, 2015).
 D. Treleavan, “Meditation, Trauma and Contemplative Dissociation,” Somatics 16, no. 2 (2010): 20–22.
 J. Compson, “Meditation, Trauma and Suffering in Silence: Raising Questions About How Meditation is Taught and Practiced in Western Contexts in the Light of a Contemporary Trauma Resiliency Model,” Contemporary Buddhism 15, no. 2 (2014): 282.
 D. A. Treleaven, Trauma-Sensitive Mindfulness: Practices for Safe and Transformative Healing (New York and London: W.W. Norton and Company, 2018).
 Treleaven, “Meditation, Trauma,” 20.
 M.K.B. Lustyk, N. Chawla, R.S. Nolan and A.G. Marlatt, “Mindfulness Meditation Research: Issues of Participant Screening, Safety Procedures, and Researcher Training,” ADVANCES 24, no. 1 (2009): 20-30.
 The authors also note that some people may fear violating their own religious principles by engaging in secular meditation practices that were originally derived from Buddhism or other religions.
 L. Burrows, “ ’I Feel Proud We Are Moving Forward’: Safeguarding Mindfulness for Vulnerable Student and Teacher Wellbeing in a Community College,” The Journal of Adult Protection 19, no. 1 (2017): 36.
 L. Burrows, “Safeguarding Mindfulness Meditation for Vulnerable College Students,” Mindfulness 7 (2016): 284.
 P.L. Dobkin, J.A. Irving and S. Amar, “For Whom May Participation in a Mindfulness-Based Stress Reduction Program be Contraindicated?” Mindfulness 3 (2012): 44-50.
 Dobkin et al., “For Whom,” 44-50.
 B.M. Wilson, L. Mickes, S. Stolarz-Fantino, M. Evrard and E. Fantino, “Increased False-Memory Susceptibility After Mindfulness Meditation,” Psychological Science 26, no. 10 (2015): 1567-1573.
 In this study ‘criminal thinking’ refers to ‘criminogenic cognitions,’ which are defined as thought patterns used to reduce the dissonance between moral standards and behaviour, rationalise deviant behaviour, and minimise negative consequences. J.P. Tangney, A.E. Dobbins, J.B. Stuewig and S.W. Schrader, “Is There a Dark Side to Mindfulness? Relation of Mindfulness to Criminogenic Cognitions,” Personality and Social Psychology Bulletin 43, no. 10 (2017): 1415–1426.
 J.R. Lindahl, N.E. Fisher, D.J. Cooper, R.K. Rosen, and W.B. Britton, “The Varieties of Contemplative Experience: A Mixed-methods Study of Meditation-related Challenges in Western Buddhists,” PLoS ONE 12, no. 5 (2017): 1.
 W. Britton, “The Dark Side of Dharma,” Buddhist Geeks (2011), accessed 24 October 2016: https://art19.com/shows/buddhist-geeks/episodes/bb6cd056-ca75-42e0-bead-2d8d862aa46f.
Britton, “The Dark Night Project,” Buddhist Geeks (2011), accessed 24 October 2016: https://art19.com/shows/buddhist-geeks/episodes/7c66e68d-ab9b-4a08-a21a-caa8d8a724f9.
Jenkins, “Is Mindfulness Meditation Dangerous?” BBC Radio 4 (2016), accessed 24 October 2016: http://www.bbc.co.uk/programmes/articles/2nB1psRz3JFQpzDh6J2Z6xl/is-mindfulness-meditation-dangerous.
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