In light of the high degree of psychiatric and cognitive symptoms present in Parkinson's disease (PD) sufferers, researchers have reviewed the efficacy of various therapies used to treat depression and anxiety in PD patients.
Curtin University School of Psychology and Speech Pathology lead researcher Dr Lakkhina Troeung says depression affects up to 75 per cent of PD sufferers while anxiety is experienced by 30-40 per cent of patients.
"Studies from all over the world have shown that depression and anxiety are consistently rated by patients as more detrimental to well-being than motor symptoms, even in the most advanced stage of illness where motor symptoms have fully progressed," she says.
"But despite this, the main focus of treatment and research in PD remains on motor symptoms.
"Our aim was to integrate all the available scientific information on the treatment of depression and anxiety in PD, in order to guide clinical care."
From the 29 randomised controlled trials uncovered after a comprehensive literature search, nine randomised placebo-controlled trials were eligible for analysis.
These trials involved both pharmacological (antidepressants) and non-pharmacological treatments including Omega-3 fatty acid supplementation and cognitive behavioural therapy (CBT).
Dr Troeung's analysis calculated the pooled effect size (the strength of an outcome from an experimental intervention) of antidepressant therapies for the treatment of depression in PD; the first meta-analysis to do so.
"Our review showed the pooled effect of antidepressants in PD, while statistically non-significant, was large, suggesting they are beneficial," she says.
In terms of non-pharmacological treatments, both Omega-3 supplementation and CBT had significant effects on depression, and CBT showed an additional secondary effect on anxiety.
The CBT trial also resulted in the largest reduction in depression over all other treatments.
"This is really promising," she says.
"People with PD take up to five medications just to manage their PD; adding antidepressants can be very dangerous…it would be much safer to offer a non-pharmacological alternative."
Dr Troeung stresses that the limited research available makes it difficult to make any substantive conclusions but says "…the overall message [from our review] is that any treatment, pharmacological or non-pharmacological, is better than no treatment."
"In all of the trials, those who were treated demonstrated better outcomes than placebo, no matter how small the difference."
Dr Troeung highlights the need for more clinical trials on antidepressants to determine their efficacy in PD, as well as further research on non-pharmacological treatments as safer alternatives.
"A meta-analysis of randomised placebo-controlled treatment trials for depression and anxiety in Parkinson's disease." Troeung L, Egan SJ, Gasson N. PLoS One. 2013 Nov 13;8(11):e79510. DOI: 10.1371/journal.pone.0079510. eCollection 2013.