@Spanglebangle
I know two people who have taken mirtazapine both of them got very fat very quickly and were miserable because of it. For both of them sertraline worked without the fattening.
Personally I wouldn't take mirtazapine.
I think if your depression or mental health condition is characterised by insomnia (I've only just taken my tablet, I usually take it around 9pm) then it's worth a go. In the US and Canada, if the patient puts on weight rapidly, buproperion is commonly prescribed alongside it if the patient is already obese, but it's not here because buproprion is only licensed for smoking cession and only for a limited time, even if you are under the care of a private psychiatric consultant. But in the UK, it's usually recommended where the patient has insomnia characterised by not being able to get off to sleep at all.
Personally, I actually got on with zopiclone well, but it's nigh on banned here so I went for this.
I researched and found it was associated with increased appetite, so decided to try it with that in mind. I was a serious mess, though. I was past idealising suicide and to the point of planning it with several methods in place or else so clear on intent I could wait to get back to N. America and dispatch myself with a firearm which would eliminate the need for several methods. A trained arm with a gun will do the trick.
I did put on weight, but as pointed out, that effect attenuates, and I'm alive to tell the tale and on track to losing the weight.
I experienced far fewer side effects than with sertraline, citalopram or fluoxetine.