Mainly the mood stabilizers like Lamictal and antipsychotics like Abilify. There's evidence they downregulate T4/T3 conversion, dialing back your metabolic rate even with no change to caloric intake. If you're stuck on these fucking drugs, get your free T3 checked (NOT TSH) and add Cytomel to fix the deficit.  Abilify sucks. I took it for 2 months.