Impulsive behaviour: too much of a good thing?
Whilst helping with the movement symptoms of Parkinson’s, drugs that mimic the effects of dopamine in the brain can result in worrying behaviours. Problems with impulsive behaviour are quite rare, but can have a big impact on those affected.
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Impulse control behaviours (ICBs) are characterised by a lack of self-control of certain emotions or behaviours. When these behaviours are more severe they are classed as impulse control disorders (ICDs). Both ICBs and ICDs are behaviours that continue despite causing some kind of harm, either to the affected individual or to those around them. Some examples of how this behaviour may manifest is excessive gambling, shopping or hypersexuality.
Around 14% of people with Parkinson’s experience ICDs. ICBs are likely to affect more people and be under-reported by people with Parkinson’s, perhaps because of embarrassment, or a lack of understanding that these behaviours are linked to Parkinson’s.
Julie, one of our Patient and Public Involvement volunteers, shares her story of impulsive behaviour:
Buying shoes — is this ever not obsessive for us girls?
Well, for me, I was the exception to the rule. Until I was 55 years old, I hated buying shoes. It was the thought of trying on shoes that were never as comfortable as old well panned in favourites.
So, what changed? Well, I was diagnosed with Parkinson’s, and was prompted to start looking for shoes that could accommodate my toes scrunching up, but that I still liked. I went from small heeled court shoes, to Mary Jane’s, and then back to flat court shoes, with several experiments with sandals along the way, particularly when there were reductions as this gave me permission to buy them because they were such a good deal!
It became a routine, always taking an interest in shoes wherever I was. Perhaps it was something to do with “having in” a range of shoes, in a range of colours, and in a range of different styles. I went from about 8 pairs of shoes, to 50! Maybe this is not a lot for many women, but for me, and an uncharacteristic parting with a few hundred pounds, this was a new pattern of behaviour.
I had moved into late night internet shopping, and became tangled up in the enticing adverts on the side bar of the web page, regardless of what I was originally looking at.
Having become aware of impulsive behaviour linked with Parkinson’s, and a discussion with my Parkinson’s nurse, I recognised that I needed to take control of this behaviour.
What causes impulse control disorders?
Whilst Parkinson’s itself does not make someone more likely to have impulsive behaviour, a class of Parkinson’s drugs called dopamine agonists, are associated with these behaviours. Not everyone who takes dopamine agonists will experience these behaviours— whether someone will develop impulsive behaviour is a complex interaction between many factors. Risk factors for ICDs include being a younger male, being unmarried and having a family history of addictive behaviours.
In Parkinson’s, the dopamine-producing cells in the substantia nigra in the brain are lost over time. Current Parkinson’s drugs remedy this by increasing the levels of dopamine in the brain. Dopamine agonists are a class of drugs that stimulate the dopamine receptors, and therefore mimic the effects of dopamine.
D1, D2 and D3 are three of the dopamine receptors in the brain. Receptors D1 and D2 are are involved in the motor circuit. When these receptors are not activated, because of a lack of dopamine, tremor, stiffness and the other movement symptoms of Parkinson’s emerge.
The D3 receptor is involved in the reward circuit. The role of dopamine at this receptor is to encourage rewarding behaviours. When this receptor isn’t receiving enough dopamine, people may experience a lack of motivation, and experience apathy.
Dopamine agonists can help to relieve the motor symptoms of Parkinson’s by acting on D1 and D2 receptors. But when dopamine agonists act on the D3 receptors, they can ‘overdose’ the reward pathway and cause increased risk-taking and impulsive behaviours.
Managing impulsive behaviour — a balancing act?
If impulsive behaviour becomes a problem for people affected by Parkinson’s, they may need to reduce the dose of their dopamine agonist medication. However this can leave their other symptoms of Parkinson’s less well treated.
This is what led Jade Pickering, Dr Ellen Poliakoff, Dr Jen McBride and Professor Ira Leroi to explore whether there was an alternative way to manage impulsive behaviour.
Jade’s research, at the Body Eyes and Movement lab at the University of Manchester, aims to find out whether a home-based intervention on a tablet computer can help people with Parkinson’s who have an ICD to control their behaviour. The participants will practice ‘stopping behaviours’, which Jade explains:
It’s thought that areas of the brain involved in resisting risky (but rewarding) behaviours, such as those in ICDs, overlap with the areas of the brain associated with the control of simpler actions. Therefore, practising stopping yourself from tapping (“control of action”) on a screen when you see a “stop” cue might generalise to stopping yourself from engaging in risky behaviours over longer periods of time.
Jade explains what the study will involve:
This will involve a simple game-like task where the participants must tap on the screen as quickly as they can when they see a “go” cue (for example a green circle) and try not tap on the screen when they see a “stop” cue (a red circle). This is trickier than it sounds, because the circles appear one after another very quickly, so it becomes quite difficult to stop yourself from tapping when you see the “stop” cue!
Jade’s research will be the first to examine the effect of practising stopping behaviours in Parkinson’s, though some research has explored this in other fields. Practising stopping behaviours can help adults to reduce risky gambling decisions in the short term. And an app that uses stopping behaviours had some success in reducing impulsive eating.
Jade is hoping that practising the control needed in the game will help people to exert more control over their impulsive behaviour and reduce the severity or frequency of the behaviours in people with Parkinson’s. Additionally, Jade’s team will be looking at whether the study has any impact on well being, anxiety, depression and feelings of control.
We will interview the participants before the study starts to find out about their ICD, strategies they’ve tried, and where they would like to see themselves in the future. After practising for several weeks, we will speak to them again to gain insight into their thoughts about participating, and what they liked and didn’t like.
If the results from this phase of the study look promising, Jade intends to broaden the research out to further participants.
We intend to start small, refine our plans as best as possible, and then broaden out to testing it with many more people with ICDs. It will be important to capture whether our intervention works for all ICDs or only specific behaviours (e.g. gambling). If, after further work, it still looks promising, we will look to make the app available to people with Parkinson’s to use in their own time.
Our helpline and local advisers can support anyone with Parkinson’s, their family or friends. Call 0808 800 0303 to get in touch.
People affected by Parkinson’s were involved in designing Jade’s study. To hear about opportunities to help shape research, join the Research Support Network today.
