The adverse effects of meditation as reported in scientific studies are as follows:
- relaxation-induced anxiety and panic
- paradoxical increases in tension
- less motivation in life
- impaired reality testing
- confusion and disorientation
- feeling 'spaced out'
- increased negativity
- being more judgmental
- feeling addicted to meditation
- uncomfortable kinaesthetic sensations
- mild dissociation
- feelings of guilt
- psychosis-like symptoms
- destructive behavior
- suicidal feelings
Also, anecdotal evidence suggests that meditation can worsen symptoms of some psychiatric problems.
Study from 1992:
Adverse effects of meditation: a preliminary investigation of
long-term meditators, by Shapiro DH Jr.
Department of Psychiatry and Human Behavior, California College of Medicine, University of California, Irvine.
Adverse effects of meditation were assessed in twenty-seven long term
meditators (average 4.27 years) both retrospectively (time one) and
prospectively at one month (time two) and six months (time three)
following a meditation retreat. At both time one and time three
subjects reported significantly more positive effects than negative
from meditation. However, of the twenty-seven subjects, seventeen
(62.9%) reported at least one adverse effect, and two (7.4%) suffered
profound adverse effects. When subjects at time one were divided into
three groups based on length of practice (16.7 months; 47.1 months;
105 months) there were no significant differences in adverse effects.
How the data should be interpreted, and their implications both for
the clinical and psychotherapeutic use of meditation as a
relaxation/self-control strategy, and as a technique for facilitating
personal and spiritual growth, are discussed. Limitations of the study
and suggestions for future research are also offered.
Meta-analysis from 2000:
Meditation: concepts, effects and uses in therapy by Alberto
Perez-De-Albeniz and Jeremy Holmes
International Journal of Psychotherapy, Mar2000, Vol. 5 Issue 1,
Abstract: This article reviews 75 scientific selected articles in the
field of meditation, including Transcendental Meditation among others.
It summarizes definitions of meditation, psychological and physiological
changes, and negative side-effects encountered by 62.9% of meditators
studied. While the authors did not restrict their study to TM, the
side-effects reported were similar to those found in the "German
Study" of Transcendental Meditators: relaxation-induced anxiety and
panic; paradoxical increases in tension; less motivation in life;
boredom; pain; impaired reality testing; confusion and disorientation;
feeling 'spaced out'; depression; increased negativity; being more
judgmental; feeling addicted to meditation; uncomfortable kinaesthetic
sensations; mild dissociation; feelings of guilt; psychosis-like
symptoms; grandiosity; elation; destructive behavior; suicidal
feelings; defenselessness; fear; anger; apprehension; and despair.
Official recommendations in the US:
Side Effects and Risks
Meditation is considered to be safe for healthy people. There have
been rare reports that meditation could cause or worsen symptoms in
people who have certain psychiatric problems, but this question has
not been fully researched. People with physical limitations may not be
able to participate in certain meditative practices involving physical
movement. Individuals with existing mental or physical health
conditions should speak with their health care providers prior to
starting a meditative practice and make their meditation instructor
aware of their condition.