Ketamine has three distinct effects which are a function of dose. At medium doses it’s a recreational psychedelic and at large doses it’s an anaesthetic. Its highest efficacy against depression is seen in the micro-dose range, before any perceptual (psychedelic) effects start.

At that dose, it causes a rapid release of neurotrophic factors, which restores the function of neuronal spines. Those spines are typically damaged by chronic exposure to stress. It may not necessarily be supported by a verbal insight into your emotional difficulties, although the brief period of neuroplasticity can lead to that.

There is usually complete relief from depressive symptoms within 24-48h, but it only lasts for as long as chronic exposure to stress doesn’t start again. In some patients this means that symptoms can return within a couple of weeks, unfortunately.