It is refreshing to read of a study (particularly in a medical journal) which focuses on non-medical interventions in Parkinson's Disease. Having recently completed a Masters dissertation which sought to assess the efficacy of psychotropic medication in treating non-motor symptoms of Parkinson's, it is important for medics to be aware of alternative methods of addressing such issues.

Depression is a major non-motor complication of Parkinson's Disease, and contributes significantly to diminished social, occupational and interpersonal functioning, and carer burden. Parkinsons UK (the leading Parkinson's Disease charity in the UK) advocates regular exercise in the form of a "structured physical activity programme" to help combat depression, and indeed produces its own exercise DVD and booklet ("Keeping Moving") (1). As mentioned in van Nimwegen et al's article, exercise may help improve symptoms of depression in Parkinson's Disease (2). I therefore wondered whether the authors considered evaluating their recruited participants for symptoms of depression at baseline (by way of a validated structured depression rating scale), and ascertaining whether there was any improvement in symptomatology scores for those who were identified as depressed at the outset? It could be conceivable that whilst their particular physical activity programme did not show statistical evidence of improvement in their chosen end-points relating to physical exercise, it may have demonstrated increased efficacy as a treatment modality for depression, as compared to the active comparator arm.

However, van Nimwegen et al's article reports that it's exclusion criteria included "those with co-morbidity that interfered with daily functioning." It is not clear whether depression qualifies as one of these co-morbidities, and is therefore not clear whether those with depression were excluded from the outset.

I feel this would have been a shame, as the evidence-base for the use of exercise in treating depression in the context of Parkinson's Disease still needs some consolidation, to back it's sounds face validity. This is particularly pertinent given that many sufferers of depression with Parkinson's respond sub-optimally to antidepressant medication. Alternative treatment modalities with a robust evidence-base are thus crucial.

(1)http://www.parkinsons.org.uk/PDF/FS56_DepressionandParkinsons.pdf
(2) Speelman AD, van de Warrenburg BP, van Nimwegen M, Petzinger GM, Munneke M, Bloem BR. "How might physical activity benefit patients with Parkinson disease?" Nat Rev Neurol 2011;7:528-34.

Competing interests: None declared