Chronic ketamine abuse causes diffuse brain damage visible on MRI. In 21 addicts with 0.5 to 12 years of use, lesions appeared in multiple brain regions after 2–4 years of addiction. Cortical atrophy was evident in the frontal, parietal, and occipital cortices. The pattern of injury differs from that caused by cocaine, heroin, or methamphetamine.
Long-term recreational ketamine use is associated with lower gray matter volume, reduced white matter integrity, and decreased functional connectivity between brain regions, particularly thalamocortical and corticocortical pathways. A systematic review of 16 studies involving 440 chronic users (average 2.4 grams per day for 2–9.7 years) compared with 259 drug-free controls and 44 poly-drug controls found these neuroanatomical differences. The observed brain changes may help explain cognitive and psychiatric side effects of prolonged ketamine abuse, including memory impairment and executive functioning problems. The findings suggest that efforts to curb ketamine abuse are warranted given its potential long-term effects on the brain.
Chronic social isolation in marmosets leads to significant shrinkage of neurons in the striatum, a brain region that integrates emotion, motivation, and movement. Ayahuasca, a psychoactive plant-based brew, given before and during isolation, prevented this neuronal volume loss. The caudate and putamen of socially isolated animals treated with ayahuasca showed neuron sizes comparable to those of family-housed controls, while untreated isolated animals had markedly smaller neurons. The findings suggest ayahuasca may act as a prophylactic buffer against stress-induced structural brain changes.
Individuals with recurrent isolated sleep paralysis (RISP) show notable brain changes, including an increased cerebellar vermis height and a larger midbrain-pons junction. In a study of 20 participants (10 with RISP, average age 24.7; 10 controls, average age 26.3), MRI scans revealed these significant morphological differences, suggesting an over-compensatory mechanism in the brain's regulatory pathways. Despite these findings, no major variations in overall sleep structure were observed between the two groups, indicating that RISP may involve specific brain adaptations rather than broader sleep disturbances.