This study looks at how *mirtazapine*, a medication, affects anxiety in people with Parkinson's Disease (PD). The study lasts for 12 weeks and takes place at a hospital's Movement Disorders Clinic. It is a double-blind study, meaning neither the patients nor the researchers know who is getting the actual medication or a placebo (a pill with no medicine). Mirtazapine is given in a dose of 15 mg once a day. The study checks for anxiety, depression, fatigue, sleep issues, and quality of life at the start, 4 weeks, and 12 weeks into the study.

• The study lasts 12 weeks and involves several visits to the clinic.
• Participants must be over 17 years old with mild/moderate Parkinson's Disease.
• People with certain medical histories like major depression, cardiovascular disease, or recent use of certain medications cannot join.