Something to look forward to -- better mood, less stress, and less anxiety in the long run

When the mood of smokers is measured before and after quitting, their mood typically worsens during the first few days of abstinence, and then returns to previous levels within about four weeks. In studies which have continued to measure these quitters' mood over a longer period, the general finding is that it continues to improve above the level when they were smoking. Similarly, it has been found that smokers who manage to quit for six months report a steady reduction in stress from the first month of abstinence, such that six months after quitting their stress levels are lower than when they smoked...

It is evident that smokers perceive that smoking helps alleviate negative mood states, but the available evidence suggests that the only negative mood state so alleviated is that resulting directly from the nicotine dependence itself. Thus, the nicotine in tobacco relieves nicotine withdrawal symptoms, but does not have mood enhancing properties in non-addicted individuals. If anything, the experience of being addicted to tobacco appears to add to, rather than relieve, stress in the everyday lives of smokers...

There has also been debate about whether increased anxiety should be included as a withdrawal symptom. Recent research suggests that it should not because it has been found that anxiety levels actually fall rather than rise among totally abstaining smokers (as opposed to those who might have had minor lapses). Some studies have reported an initial elevation in anxiety after stopping smoking, but this is short-lived and followed by a drop to below the levels while smoking. It has been argued that the increase in anxiety observed in some studies on cessation of smoking is a psychological response to the attempt to stop, which is made worse when that attempt is not being wholly successful. This is an issue that requires clarification.

-- Royal College of Physicians