(2) Who are we looking for to take part in the study?

This is an observational and imaging study where we will follow-up patients, at different stages of Parkinson’s disease, for one year. We are aiming to recruit around 200 participants:

• 150 with Parkinson’s disease (at least 50 whom will have significant anxiety).

• 50 age-matched controls without Parkinson’s disease (25 with anxiety).

Note: 50 participants from the total sample will also have an optional MRI scan.

Key Inclusion Criteria

· Diagnosis of Parkinson’s disease

· 18 - 89 years.

· Can tolerate behavioural and psychological testing.

Key Exclusion Criteria

· Past/present psychotic disorder, bipolar disorder/mania, or alcohol/substance use disorder (outside a comorbid psychiatric episode).

· History of medical illness that may impair cognitive function (e.g., head injury, endocrine disorder)

· Atypical or symptomatic parkinsonian syndrome

Subgroup with MRI: exclusion criteria

· MRI contraindications such as a pacemaker, aneurysm clip, cochlear implant, neurostimulator, IUD, shrapnel, metal fragments in the eye, a weight of above 250lbs or claustrophobia

· Women who are pregnant, planning pregnancy, or breastfeeding