Smoking causes depression !

Smoking has long been linked with depression, though it's a chicken-or-egg scenario: People who are depression-prone may be more likely to take up the habit.

However, nicotine is known to affect neurotransmitter activity in the brain, resulting in higher levels of dopamine and serotonin (which is also the mechanism of action for antidepressant drugs).

This may explain the addictive nature of the drug, and the mood swings that come with withdrawal, as well as why depression is associated with smoking cessation. Avoiding cigarettes—and staying smoke free—could help balance your brain chemicals.