A new study reveals that nearly half (47 percent) of people who use marijuana regularly and/or heavily experience cannabis withdrawal syndrome when they try to quit. It is widely believed that the drug is not addictive, but this meta-analysis involving 23,500 participants sets that myth to rest.

Marijuana withdrawal symptoms include nervousness, anxiety, sleeplessness, depression, restlessness, and irritability. They can also include physical symptoms like stomach pain, shakiness, tremors, sweating, fever, chills, and headaches.

Experts have known for some time that marijuana is addictive, but it was confirmed in 2013 when the latest edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) was published. The manual recognized cannabis withdrawal syndrome as a bona fide disorder.