About 30% of meditators experienced challenging or distressing effects, and 9% reported functional impairment.

Evidence

Systematic review and individual participant data meta-analysis of … (Nature)

corroborated: 2 independent passages support this claim
XREF: connects to: Mindlessness leads to panic and detrimental behavior. — Dan Harris, 10 percent Happier, 40; Anxiety, traumatic re-experiencing, and emotional sensitivity were the most common MRAE; 10.6% reported some functional impairment. — Prevalence of meditation-related adverse effects in a population …; Recent studies reveal that 25–87% of those who engage in meditation report adverse effects, with 3–37% experiencing functional impairment. — Adverse effects of meditation and mindfulness in clinical practice (+1 more)

Anxiety, traumatic re-experiencing, and emotional sensitivity were the most common MRAE; 10.6% reported some functional impairment. (similarity 0.96)
Recent studies reveal that 25–87% of those who engage in meditation report adverse effects, with 3–37% experiencing functional impairment. (similarity 0.94)
At least 25% of regular meditators have experienced adverse effects from mindfulness. (similarity 0.88)
58% of 96 participants reported at least one meditation-related adverse effect, ranging from perpetual hypersensitivity to nightmares. (similarity 0.87)
Meditation and mindfulness, widely perceived as stress-reduction techniques, can also have adverse effects. (similarity 0.85)
Studies have described adverse events such as anxiety, pain, and psychosis associated with mindfulness meditation. (similarity 0.83)
The most common adverse effects are anxiety and depression, followed by psychotic or delusional symptoms and dissociation. (similarity 0.83)
Meditation practice in MBPs is associated with transient distress and negative impacts at similar rates to other psychological treatments. (similarity 0.82)
A new harm monitoring study investigates the adverse effects of mindfulness-based practices. (similarity 0.78)