Bupropion is most commonly used for treating depression and as an aid for smoking cessation. The medicine is also used in the treatment of major depressive disorder and Seasonal Affective Disorder (SAD).It works by balancing the brain chemicals to help improve patients' moods and general well being. Bupropion is frequently used to treat clinical depression because unlikr other antidepressants, it does not cause sexual dysfunction and weight gain. The medicine must be taken regularly and may take about 4 weeks to show complete results. It is not advised to stop taking the medicine abruptly as it may cause symptoms to worsen.