Parkinson’s Disease and Depression

Depression is common in patients with Parkinson’s disease (mean prevalence 17% in patients with Parkinson’s). It can be the first sign of the disease. It can be treated with antidepressants. There is little evidence that patients with Parkinson’s disease might benefit more from anyone particular class of antidepressants than any others. The problem with that is side-effects and interactions with the Parkinson medication. ECT is an option for the treatment of depression in Parkinson’s disease. It also helps for the motor symptoms although mostly temporary. As the disease progresses the motor symptoms return or become worse and here is when the Inspire support groups help in all these health issues.

Since Parkinson’s disease is mainly caused by the degeneration of parts of the dopaminergic system, antidepressants working on dopamine, dopamine agonist, might be useful for the treatment of depression in patients with Parkinson’s.
Recently a dopamine agonist was studied as treatment for depression in patients with Parkinson’s disease. Dr Shock favors placebo controlled trials. These are the trials of which we clinicians learn the most. The dopamine agonist studied was pramipexole.

Sustained administration of pramipexole can modify the spontaneous firing of dopamine, norepinephrine, and serotonin neurons in rat brains, suggesting that the therapeutic action of pramipexole might be attributed to increased dopaminergic and serotoninergic neurotransmission in the brain

This study was a 12 week randomized, double-blind, placebo controlled trial. Pramipexole was given in a dose of 0.125-1.0 mg three times per day and compared to placebo in patients with mild to moderate Parkinson’s disease. Patients from 76 centres in 12 European countries and South Africa were included if they were on stable antiparkinsonian therapy without motor fluctuations and had depressive symptoms.

The main outcome criterion was the decrease of the Beck Depression Inventory, a self rating severity scale for depression. BDI scores in the pramipexole group decreased from a mean of 18·7 at baseline to 13·1 at 12 weeks, compared with a decrease from 19·2 to 15·0 in the placebo group. . When adjusted for confounding variables the difference between the two conditions were only 2 points. This difference was significant but is it also clinical relevant?.

The problem with this study is that the focus was on depressive symptoms instead of depression. They used the Beck Depression Inventory and the geriatric depression scale for inclusion. Both screening and severity scales for depression not diagnostic scales. Also the use of their outcome criteria are hard to compare with the usual outcome in depression treatment studies. Mostly in these study diagnostic scales are used for inclusion and response is mostly defined by a 50% decrease in Hamilton Depression Rating Scale score. A better outcome criteria is remission which is mostly defined as a score of 10 or less on the 17 item version of the Hamilton Depression Rating Scale.

Although these results may seem promising as a scientist I really regret the lack of diagnosing depression and using not only self rating scale but also clinician rating scale. What do you think?
Bxarone P, Poewe W, Albrecht S, Debieuvre C, Massey D, Rascol O, Tolosa E, & Weintraub D (2010). Pramipexole for the treatment of depressive symptoms in patients with Parkinson’s disease: a randomised, double-blind, placebo-controlled trial. Lancet neurology, 9 (6), 573-80 PMID: 20452823