Brazilian researchers gave fish oil pills for a period of three months to patients with Parkinson's disease who were diagnosed with depression. The patients taking fish oil supplements had improvements in their depressive symptoms. Fish oils are also helpful in women after menopause in terms of mood elevations, see http://www.raysahelian.com/menopause.html.
Comments: It is not clear how fish oils would interact, if any, with medications currently used for PD. I don't suspect taking 3 or 4 fish oil capsules would interfere with these medications. Mucuna pruriens is an herb that is recommended by some doctors for PD. I don't think there would be a problem combining the fish oils and mucuna pills. See http://www.raysahelian.com/parkinson.html for more information and discuss with your doctor before making changes to your medication regimen.