THC in marijuana overwhelms the cannabinoid receptors and produces ravenous hunger and faulty memory. The morphine molecule locks with the opioid receptors to produce euphoria and numb pain. Opioid receptors in our lungs govern breathing; too much morphine molecule shuts down breathing, which is how overdose victims die. The morphine molecule also produces constipation in addicts. In withdrawals, without the drug, addicts suffer diarrhea. (Naloxone, the overdose antidote, is occasionally used to treat constipation.)
