Would it be so that stock buy backs amplify the company stock value during good times? But is the reverse true when there is a down turn in the market? Ie when

Would it be so that stock buy backs amplify the company stock value during good times? But is the reverse true when there is a down turn in the market? Ie when there is a market down turn if a company owns its own stock it amplifies the down movement? Can someone who understands this better explain how it works?