Because of the widely varied effects of marijuana, it can be difficult to tell if someone is using it. The following are a few of the most common symptoms someone is on marijuana: red, bloodshot eyes, laughing inappropriately or uncontrollably, increased appetite including binge eating, particularly sweets, and a lack of energy or motivation. Marijuana is also a drug unlike many others because it has a very potent odor that’s hard to get rid of. Many people compare it to a skunk-like smell, and it can cling to hair, clothes, bedding, furniture, and other items after smoking. As with most other drugs, there are behavioral shifts that may seem subtle or gradual at first. As a person continues to abuse marijuana, these may become more prominent.