Hi, there. A lot of antidepressants can cause weight gain, Effexor being one of them, but I have not heard of Trazadone causing this. Everyone's different in how drugs affect them. If your weight gain was caused by any of these drugs, I would guess that you should start losing at some point. On the other hand, maybe the weight gain is from something else. You might want to get a physical from your regular doctor to see if something else might be going on, such as low thyroid or some other hormone imbalance.
Sorry I couldn't be of more help - I don't think there's a cut-and-dried answer to your question.
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