In a real-world clinic, intravenous ketamine reduced depressive symptoms in patients with treatment-resistant unipolar and bipolar depression. Both groups improved significantly, but those with bipolar depression showed faster and greater improvement starting at two weeks and lasting through three months. Dissociative side effects were mild and did not increase over time; women with unipolar depression reported higher dissociative symptoms at three months. No sex differences in antidepressant efficacy were found. The findings suggest ketamine is effective for treatment-resistant depression, with stronger benefits for bipolar depression.
Depression likely arises from a mix of two interacting biological problems: imbalances in monoamine neurotransmitters (like serotonin) and disruptions in glutamate signaling that impair the brain's ability to adapt and form new connections. These two systems can combine in different ways across individuals, helping explain why some people respond to standard antidepressants while others do not. Rapid-acting treatments such as ketamine work by directly targeting the glutamate system to boost synaptic plasticity, offering faster relief, especially for treatment-resistant depression. A framework called the 'monoamine-glutamate continuum' may guide future precision psychiatry by matching treatments to each person's specific neurobiological profile.