Conventional antidepressants can take weeks to make a difference, and many people with treatment‑resistant depression are left waiting. Research into ketamine has revealed a dramatically different mechanism that helps explain its rapid effects. Neuroplasticity refers to the brain’s ability to remodel itself by forming new synaptic connections. Chronic stress and depression are associated with dendritic atrophy and loss of synapses in brain regions like the medial frontal cortex and hippocampus. This reduces the brain’s flexibility and may contribute to persistent negative mood. Ketamine is a non‑competitive N‑methyl‑D‑aspartic acid (NMDA) receptor antagonist. By blocking NMDA receptors, ketamine increases glutamate release and downstream activation of AMPA receptors, triggering a surge of brain‑derived neurotrophic factor (BDNF). This cascade promotes the formation of new dendritic spines and synaptic connections. Studies in animals and humans show that a single dose of ketamine can increase dendritic spine density and reverse stress‑induced synaptic loss within hours. In the medial frontal cortex and hippocampus, this synaptogenesis is thought to underlie ketamine’s rapid and sustained antidepressant effects. The window for neuroplasticity is especially open in the hours immediately after a ketamine infusion. Clinicians suggest that the first two to twelve hours following treatment are when the brain is most receptive to forming new pathways. During this period, engaging in mindfulness meditation, aerobic exercise, therapy sessions, journaling, reading or other cognitive activities can help reinforce positive changes and support long‑term recovery. Adequate sleep, hydration and good nutrition also support BDNF production and synapse formation. Understanding the science of neuroplasticity provides insight into why ketamine can provide fast relief. It also underscores the importance of integration: combining ketamine therapy with intentional lifestyle practices can help ensure that new neural pathways become lasting sources of resilience.