Ketamine for Treatment-Resistant Depression: 3-Year Safety Data Shows Sustained Benefits Without Cognitive Decline

Does Long-Term Ketamine Use Cause Brain Damage or Cognitive Problems?

One of the most important questions surrounding ketamine therapy for depression has been whether repeated exposure causes lasting cognitive harm. Multiple clinical studies, including randomized controlled trials and open-label follow-up studies, have examined this question. The standard protocol involves IV ketamine infusions at 0.5 mg/kg over 40 minutes, with maintenance infusions typically given weekly to monthly. Cognitive assessments in these studies—using validated batteries measuring memory, attention, processing speed, and executive function—have consistently shown no decline at therapeutic doses over treatment periods extending beyond one year.

In fact, several studies have reported modest cognitive improvements in treatment responders, likely reflecting the well-documented cognitive benefits of depression remission itself. Neuroimaging substudies have found no white matter changes or hippocampal volume loss at therapeutic doses, in contrast to the neurotoxicity observed in recreational ketamine users who consume far higher and more frequent doses. Urological complications, a well-known risk of chronic recreational ketamine abuse, have not been observed at the low doses used in clinical depression treatment. A 2019 randomized controlled trial by Phillips et al., published in the American Journal of Psychiatry, demonstrated that repeated ketamine infusions maintained antidepressant effects and were well tolerated, providing key evidence for the safety of ongoing treatment.

How Does Ketamine Compare to Other Treatments for Resistant Depression?

Ketamine has emerged as one of the most effective interventions for treatment-resistant depression studied to date. In the landmark 2006 study by Zarate et al. at the National Institute of Mental Health, a single ketamine infusion produced rapid antidepressant effects within hours—a finding subsequently replicated in numerous trials. The 2013 two-site randomized controlled trial by Murrough et al. found a response rate of 64% with ketamine versus 28% with an active placebo (midazolam) within 24 hours. These response rates compare favorably to the STAR*D trial's finding that remission rates drop to roughly 13% by the third and fourth treatment steps in patients who have already failed multiple antidepressant trials.

Access remains a significant barrier to ketamine treatment. Monthly infusions require clinical visits of 2–3 hours including monitoring, and out-of-pocket costs typically range from $400–600 per session in the United States. The FDA's 2019 approval of esketamine nasal spray (Spravato) for treatment-resistant depression expanded access through a more standardized delivery system with broader insurance coverage, though patients must still be monitored at certified treatment centers. Research suggests that sustained ketamine treatment is associated with reduced emergency department visits, psychiatric hospitalizations, and disability days. Advocates continue to push for expanded insurance coverage for IV ketamine, arguing that the cost of treatment is offset by reduced downstream healthcare utilization.