How do you help a friend who has stopped replying and withdrawn?

Withdrawal is common when someone is struggling, and the instinct to give them space often becomes absence. Low-pressure, consistent contact works better: short messages that do not require a reply, saying you are thinking of them rather than asking how they are, and specific offers rather than open ones — 'I am coming by on Sunday with food' rather than 'let me know if you need anything'. Do not take silence personally or stop after two attempts. If you are concerned about their safety, ask directly and clearly, and involve family or a professional rather than carrying it alone.