Yes to both. Not all patients with parkinsons are alike and can have a variety of symptoms. Depression sometimes occurs early or late in course of illness. Dementia is usually a late complications and doesn't occur in everyone.
Parkinsons disease. Depression, anxiety, paranoia, hallucinations and dementia often occur in those with parkinsons disease. Many things besides parkinsons disease can cause symptoms that seem similar to parkinsons disease but are'nt related to the above symptoms.
Yes. In parkinson's diseasedementia occurs with the progression of disease, but not everybody becomes demented. Depression might occur at the beginning of the disease or later during the disease process.