Does ketamine (anesthetic and pain management medication) enhance cognitive function or intelligence?

Does Ketamine Enhance Cognitive Function or Intelligence?

Ketamine does not make you smarter and may actually impair cognitive function in healthy individuals, with evidence showing small-to-moderate impairments across all cognitive domains during acute administration. 1

Effects of Ketamine on Cognition

Acute Effects in Healthy Individuals

• Ketamine causes broad cognitive impairment across multiple domains in healthy individuals 1
• Most prominently affects verbal learning and memory
• Produces small-to-moderate deficits in:
  • Attention
  • Executive function
  • Speed of processing
  • Working memory
  • Visuospatial abilities
• The degree of impairment is dose-dependent, with higher doses causing greater cognitive deficits

Potential Cognitive Effects in Clinical Populations

Interestingly, the cognitive effects of ketamine differ between healthy individuals and those with certain clinical conditions:

• In treatment-resistant depression (TRD):

  • Some studies show improvements in working memory and visual learning memory 2, 3
  • A study of IV ketamine (0.5-0.75 mg/kg) in TRD patients demonstrated moderate-to-large improvements in:
    • Digit Symbol Substitution Test (measuring processing speed)
    • Trail Making Test-B (measuring executive function)
    • Self-reported cognitive function 2
  • Importantly, some cognitive improvements were independent of antidepressant effects

• In low-performing animal models:

  • Low doses of ketamine (0.3-3 mg/kg) improved motivation and attention in poorly performing rats 4
  • Enhanced attentional accuracy and reduced impulsive action
  • Effects were modest and primarily observed in "low performing" subjects

Neuropsychiatric Side Effects and Risks

Ketamine has significant neuropsychiatric effects that can negatively impact cognition:

• Produces psychotropic effects including hallucinations, nightmares, and psychosis 5

• These effects appear to be dose-dependent

• In perioperative settings, ketamine administration is associated with:

  • Higher delirium scores at certain doses 5
  • Increased incidence of hallucinations (20-28% vs 18% with placebo) 5
  • Increased nightmares (12-15% vs 8% with placebo) 5

• Long-term cognitive risks:

  • Animal studies suggest ketamine may cause neuronal and oligodendrocyte cell loss in developing brains 6
  • These cellular changes are associated with prolonged cognitive deficits in learning and memory 6
  • Recurrent high-dose ketamine misuse may lead to memory and attention impairment 6

Clinical Implications

• Ketamine is not recommended for cognitive enhancement in healthy individuals

• The drug primarily functions as:

  • An NMDA receptor antagonist 7
  • A dissociative anesthetic that produces a trance-like cataleptic state 5
  • An analgesic with sedative properties 5

• Ketamine should be avoided in patients with:

  • Ischemic heart disease
  • Cerebrovascular disease
  • Hypertension 7
  • History of substance abuse (due to potential for misuse) 6

Conclusion

While ketamine may have therapeutic benefits for certain psychiatric conditions like treatment-resistant depression, the evidence does not support its use for cognitive enhancement. In fact, the predominant effect in healthy individuals is cognitive impairment across multiple domains. Any potential cognitive benefits appear to be limited to specific clinical populations with pre-existing cognitive deficits, and these benefits may be secondary to improvements in underlying psychiatric conditions.