Sometimes, but not without a green light from your prescriber: ashwagandha has sedative effects that can add to the drowsiness many antidepressants cause, so combine it only under medical guidance — don't start it on your own.
NCCIH states that ashwagandha "seems to have sedative effects" and notes "preliminary evidence that it may increase the effects of some benzodiazepines (Valium) and other sedatives and anti-anxiety drugs, including Xanax," and lists sedatives among the drug classes it may interact with. Many antidepressants themselves cause drowsiness — the NHS lists "feeling dizzy, drowsy or very sleepy" as a common antidepressant side effect — so the main concern is additive sedation (excess drowsiness/grogginess) rather than a proven dangerous chemical interaction. Authoritative sources do not document a specific, well-established ashwagandha-antidepressant interaction, but they also do not clear the pair as safe, and the NHS warns that combining antidepressants with herbal remedies (it singles out St John's wort) can cause problems.
Talk to the prescriber or pharmacist who manages your antidepressant before adding ashwagandha — don't just start it. Watch for excessive drowsiness, sedation, dizziness, slowed thinking, or trouble concentrating, and be cautious about driving until you know how the combination affects you; sedation is more likely if your antidepressant is itself sedating or if you also take sleep aids, anti-anxiety drugs, or alcohol. Because rare cases of liver injury have been linked to ashwagandha, stop it and seek care for yellowing skin/eyes, dark urine, nausea, or right-upper-abdominal pain. NCCIH considers ashwagandha possibly safe only for short-term use (up to about 3 months), with long-term safety unknown. Avoid ashwagandha entirely if you are pregnant or breastfeeding, have an autoimmune or thyroid condition, take thyroid medication, are scheduled for surgery, or have hormone-sensitive prostate cancer. Do not stop or change your antidepressant on your own.
This is general reference, not medical advice, and not a guarantee of safety. Interactions depend on your doses, health conditions, and other medicines. Always confirm with your pharmacist or doctor before combining products, and follow the dosing on each label.