Abrupt termination of cannabis use can produce a mild withdrawal syndrome. Withdrawal symptoms include sleep disturbance, irritability, loss of appetite and consequent weight loss, nervousness, anxiety, sweating and upset stomach. Sometimes chills, increased body temperature and tremors occur. The withdrawal syndrome usually lasts for less than a week, although the sleep disturbances may persist for a longer period. Some frequent users have reported the return of vivid dreams, which seem to be suppressed with heavy use.