Chemical dependency builds in relation to the frequency of use, dosage, age, sex, weight, and medical condition. Once chemical dependency has developed, abrupt cessation of use will cause withdrawal; symptoms include leg and abdominal cramps, mydriasis, vomiting, diarrhea, headache, insomnia, cravings, lethargy, and anxiety. Symptoms of withdrawal usually fade after 4–10 days but cravings and psychological dependence may continue for longer, in some cases up to a year.