The forum team have asked me to post about how widespread the problem of dopamine-agonist-associated behavioural changes are.
A number of studies have now been carried out to determine this. These include problems such as pathological gambling, hypersexuality and abnormal compulsive behaviour.
The most comprehensive study was that by Weintraub in 2010 which examined over 3,000 people and found that approximately 17% of those on dopamine agonists alone, or in combination with other drugs, experienced these problems. A subsequent study by Hassan (of the Mayo Clinic) was published in 2011, although this contained a smaller number of participants (321). The overall results were similar to the previous study with 16% reporting problems.
However, when they looked at people who were on doses of drug that are generally considered as being appropriate for the treatment of Parkinson’s, this increased to 24%.
Analysing studies such as these can be difficult. It is generally accepted that the larger the study, the more accurate the data will be. So as the Weintraub study had 10 times more participants, the results are probably more accurate.
Secondly, the Hassan study found an initial prevalence of 16% of behavioural changes in all people on the medication. This only increased to 24% when they looked at a subset of the participants taking higher doses. So it appears that there is definitely an increase in the rate of the problem associated with higher doses of the drugs prescribed.
It is very difficult to determine exactly how widespread the problem is as there are many factors that can impact on the results obtained. In addition to the direct effects of the medication, we need to consider how many people in the general population actually experience these problems.
One study has suggested that this could be at least 6%. And another study has suggested that people who are diagnosed with Parkinson’s could have an even higher prevalence of these problems even before they are prescribed medication. So, a lot more research is required in this area.
Previous research suggested that people with Parkinson's may be at greater risk of impulsive and compulsive behaviour before they even start medication. But new research published in January 2013 shows that having Parkinson's alone does not increase the risk of impulsive and compulsive behaviour. It's only when people with the condition start taking the medication that the risk increases.
Parkinson’s UK has a number of initiatives in place to address this problem. These include raising awareness among doctors, nurses and pharmacists to ensure that people with Parkinson’s are made aware of the potential problems when they are prescribed the drugs and are carefully monitored for changes in behaviour.
We are also funding research in this area, including a study at the Institute of Psychiatry investigating the potential use of cognitive behavioural therapy to help people who have experienced the side effects. The initial results on a small number of people look very encouraging and we will make sure that any recommendations are made public as soon as possible.
Parkinson's UK-funded research published in February 2013 showed that talking therapy can help people with Parkinson's manage impulsive and compulsive behaviour with 3 out of 4 people in the study benefiting from therapy. You can read more in our news story Talking therapy may help manage impulsive and compulsive behaviour.
I hope this helps.
This post was updated on 6 November 2013 in light of new research available.