Anxiety
"My son was prescribed Mirtazapine for severe anxiety. It helped a little bit and also his medicine for his bi polar disorder helped (Depakote). 
However,  once the anxiety decreased he should have had the Mirtazapine stopped by the psychiatrist.  This did not happen and he eventually had a severe psychotic breakdown where he tried to smash up his home, attacked his partner and believed aliens were after him . He was in hospital for over 2 months after the police had him sectioned."