When addicted individuals stop using cocaine, they often become depressed which may lead to further cocaine use to alleviate depression.
Opiate addicted individuals need higher and higher amounts of opiates in order to prevent withdrawal symptoms and to maintain their feelings of euphoria.
Drug withdrawal symptoms from benzodiazepines can be more difficult than withdrawing from opioids.
PCP affects the area of the brain involved in the perception of pain, responses to the environment, and learning and memory.