Cannabis-withdrawal is the term for the physical and psychological effects that occur when someone stops using cannabis after regular or heavy use. These symptoms can last up to 2 weeks and include anxiety, irritability, insomnia, decreased appetite, headaches, and cravings. A cannabis hangover is another story altogether. It's a mild, short-lived condition that some people experience the day after using cannabis. These symptoms may include fatigue, dizziness, a cottonmouth, red eyes, and mild nausea, and usually fade within 24 hours.