An important and poorly understood component of nicotine withdrawal is craving or a continued urge to use nicotine. Craving has been described as a major obstacle to successful abstinence and may persist for six months or longer. While the withdrawal itself is related to the pharmacological effects of nicotine, the severity of withdrawal symptoms can also be affected by psychological experiences. For some people, the feel, smell, and sight of a cigarette and the ritual of obtaining, handling, lighting, and smoking it are all associated with the pleasurable effects of smoking and can make withdrawal or craving worse. While nicotine gum and patches may alleviate the pharmacological aspects of withdrawal, cravings often persist.