Nicotine dependence or tobacco dependence is a medical condition characterized by tobacco addiction due to the drug nicotine present in tobacco. Addiction to any substance is defined as a condition in which despite the fact that the addictive substance can take a toll on the person’s health, emotional condition, social relationship, performance at work place and also on the financial status of the person, one (the addict) craves for the addictive substance.
Nicotine causes change in the mood as well as in the physical system in a pleasant way, thus makes the person crave for the drug and ultimately it leads to dependence. Again abrupt stoppage of tobacco leads to set of bothersome symptoms, known as withdrawal symptoms. Withdrawal symptoms are characterized by irritability, increased anxiety, headache, lack of sleep (insomnia), restlessness, depression, increased tiredness, lightheadedness, increase in appetite etc.
Although nicotine present in the tobacco is responsible for all the withdrawal symptoms, other chemical substances present in tobacco are responsible for the different adverse effects of tobacco on health like increased incidence of heart diseases, stroke, certain types of cancer like lung cancer etc.
No matter for how many years one is smoking, quitting smoking always leads to positive effects on a person’s heath. There are several options which help in quitting smoking and managing the bothersome withdrawal symptoms.

Causes
Although there are several chemicals present in tobacco, nicotine is the most important chemical substance present in cigarette smoke which is responsible for addiction. Nicotine has high level of addictive property especially when it enters the lungs through inhalation. Upon entry of nicotine through blood stream in the brain leads to release of several chemicals, neurotransmitters helping in elevation of mood. Dopamine is one of the most important neurotransmitters which upon release increases the sense of pleasure (reward) and elevates the mood. Release of dopamine is not only facilitated by nicotine in the brain, in all types of addiction, the addictive substances increase the release of dopamine in the brain and thereby increase the sense of pleasure, well being etc.
There are certain characteristic features which indicate presence of nicotine dependence; these include
1. Craving of smoking at certain specific times: like after waking up in the morning, with intake of morning coffee, during work breaks etc
2. After having a meal
3. During drinking of alcohol
4. While going to certain places or meeting certain people
5. During conversation on phone
6. During facing stressful situations
7. While driving the car
8. If someone else is smoking or smelling the smoke

Risk factors
The risk factors associated with nicotine dependence include
1. People with history of smoking or use of tobacco in any form
2. Genetic factors seem to play an important in determining if a person will smoke or not, as the response of the nerve cells in the brain (release of dopamine) to nicotine is somehow dependent upon the genetic make up of the person
3. Having parents or closed family members who are smokers increases the risk of smoking.
4. Age: early age of initiation of smoking increases the risk of becoming heavy smokers
5. Suffering from any sort of mental conditions like depression, post traumatic stress disorders, etc.
6. Indulging in other addiction like alcohol or illegal drugs also increases the chance of smoking.