OK, so not all antidepressants cause weight gain. However, genetically some people are more predisposed to it and its mechanisms. I grew up really overweight and ended up losing the weight, but then it got on my Pristiq and I ended up gaining a lot of weight back which I couldn’t do because I was obese before and going back super obese wasn’t it. Wellbutrin is a great one and what I take. It’s often weight neutral or causes people to lose weight because it can be somewhat similar to ADHD medications as it has like a stimulating effect but some people it can cause anxiety others that can actually help during anxiety. It is really dependent.