Trazodone does not typically cause weight gain in patients; it is considered an infrequent side effect, according to WebMD. When weight gain does occur, it is less-severe than other infrequently occurring side effects associated with the antidepressant.
Trazodone is referred to as an atypical antidepressant due to its unique qualities and side effects, such as blurred vision, fatigue, diarrhea and irregular heartbeat, states Mayo Clinic. Since it causes drowsiness, trazodone is typically used before going to bed. Marketed as Oleptro, trazodone relieves anxiety and boosts a patient's mood by changing the balance of chemicals such as serotonin in the brain. A physician may prescribe trazodone alone or with other medications.