These older types of antidepressants affect neurotransmitters, causing a broad range of side effects
including significant weight gain
. Newer antidepressants don’t have the same side
effect. While Paxil and Zoloft do cause some weight gain, other SSRIs, like Prozac, Celexa and Lexapro, don’t. For Paxil and Zoloft, the weight gain can add up to five to 40 pounds a year. Some people do experience weight gain with Lexapro or Celexa, but most don’t.