Nicotine - increases activity of the central nervous system Alcohol - causes sleepiness, decreases activity in central nervous system "Speed" - loss of appetite; increases activity in the central nervous system Xanax - decreases anxiety, induces sleep Darvon - gives a sense of euphoria and well-being; blocks out pain/problems Caffeine - helps one stay awake and feel more alert Hydrocodone - relieves pain and causes drowsiness - Mescaline - distorts perception and thinking Peyote - alters senses, visual illusions Nicotine - increases activity of the central nervous system Alcohol - causes sleepiness, decreases activity in central nervous system "Speed" - loss of appetite; increases activity in the central nervous system Xanax - decreases anxiety, induces sleep Darvon - gives a sense of euphoria and well-being; blocks out pain/problems Caffeine - helps one stay awake and feel more alert Hydrocodone - relieves pain and causes drowsiness Mescaline - distorts perception and thinking Peyote - alters senses, visual illusions - Nicotine - increases activity of the central nervous system Alcohol - causes sleepiness, decreases activity in central nervous system "Speed" - loss of appetite; increases activity in the central nervous system Xanax - decreases anxiety, induces sleep Darvon - gives a sense of euphoria and well-being; blocks out pain/problems Caffeine - helps one stay awake and feel more alert Hydrocodone - relieves pain and causes drowsiness - Mescaline - distorts perception and thinking Peyote - alters senses, visual illusions Nicotine - increases activity of the central nervous system Alcohol - causes sleepiness, decreases activity in central nervous system "Speed" - loss of appetite; increases activity in the central nervous system Xanax - decreases anxiety, induces sleep Darvon - gives a sense of euphoria and well-being; blocks out pain/problems Caffeine - helps one stay awake and feel more alert Hydrocodone - relieves pain and causes drowsiness Mescaline - distorts perception and thinking Peyote - alters senses, visual illusions