I was prescribed an anti-psychotic because I was having hallucinations and severe dissociation--psychosis brought on my extreme stress. If you are under extreme stress and they are trying to head off major cognitive distortions, that could be why. They had a "deadening" effect, which I hated, but the hallucinations stopped and then we could get to more "normal" symptoms. When I dissociate, nothing sticks--I can't even remember what I was doing two hours ago, let alone what some therapist told me.
ASAP, other meds were added, tweaked, changed, added. It took a good year to find the right mix...closer to two years, really. (Lamictal and tegretol and some little ones to help with vitamin deficiencies--which are common for us)