A drug is any substance that causes a change in an organism's physiology or psychology when consumed.Drugs are typically distinguished from food and substances that provide nutritional support. Consumption of drugs can be via inhalation, injection, smoking, ingestion, absorption via a patch on the skin, or dissolution under the tongue.These categories are: stimulants, inhalants, cannabinoids, depressants, opioids, steroids, hallucinogens, and prescription drugs. There is a common misconception that these drugs that have opposite effects (such as stimulants and depressants) have the ability to cancel each other out.