Is remeron (mirtazapine) used for generalised anxiety disorder. thanks?

Not quite: Mirtazepine is a very useful antidepressant that is also helpful for insomnia, especially secondary to a depressive disorder. Sometimes, some doctros prescribe it to enhance the deep (restful) phase of sleep. However it is not known for its effcacy to relief anxiety, except as secondary to a clinical depression. Depending clinical presentation, Alprazolam or Paroxetine are more suited for anxiety

Remeron & GAD: I tend to see it used the most in patients with insomnia. It can cause significant drowsiness so I don't see it used very often as an antidepressant.