Does mirtazapine cause weight gain?

Hi, Wheel!
Yes, as with most pyschotropic medications mirtazapine has the potential to cause weight gain in a little more than 10% of users:
"Metabolic
Very common (10% or more of users): Increased appetite (up to 17%), weight gain (up to 12%)"
Because it can cause an increase in appetite weight gain can be minimized with a healthy diet and exercise.
"Commonly reported side effects of mirtazapine include: sedation, constipation, drowsiness, , weight gain, fatigue, increased appetite, and decreased appetite. Other side effects include: dizziness, tremor, dyspepsia, palpitations, vertigo, abnormal dreams, and bitter taste"
Most people don't have side effects and if they do they're generally mild and resolve within days to a week or so. Don't be afraid that you'll have them all... you won't.

Common mirtazapine side effects include:

drowsiness, dizziness;

increased appetite; or

weight gain.

https://www.drugs.com/mirtazapine.html