Dimentia

So my dad was diagnosed with parkinson about 18 years ago. All he really had was a little hand tremor and it never progressed, we feel he may have been misdiagnosed. Anyway about 4 years ago he feel and was never able to balance again( his legs are really strong) but can walk with assistance, he also seem to have become demented at that same point . We think maybe it is not dementia( does that really come on so acutely?). So......can taking lexapro , clonazapram and carbidopa/levadopa interact and known to cause any neurological issues? A few years ago my sister went to a doc visit and for some reason another neurologist at the place( forget the scenario) said they would never prescribe one of those antidepressants(forget which one) with the PD meds. Thanks for any insight..