Sudden Addiction to Gambling, Loss of Control Over Shopping and a Raised Sex Drive Are Mostly Parkinson's Medicine Side Effects, and Do Not Mean the Person's Character Has Broken Down

An older man who has been thrifty and honest for most of his life suddenly, after starting Parkinson's medicine, shops online compulsively, gambles in secret, and even has a sexual drive so much higher that his spouse complains of being troubled. The first reaction of many families is often: "Has he become a different person?" Some suspect that the older adult has "gone bad in old age". This article aims to clarify one important fact: such unusual behaviour is very likely not a breakdown of character, but a drug side effect supported by large studies, which medicine calls an "impulse control disorder" (ICD).

This is a sensitive subject that can easily break up a family, yet public education about it in Hong Kong is almost a blank. The sections below therefore explain in detail the cause of this side effect, the high-risk groups and how families can recognise it, and stress three most important principles: do not scold, tell the doctor as soon as possible, and do not stop the medicine alone.

First, the position of this page. This article gives educational information for carers from the occupational therapy point of view, and gives no guidance on changing medicines. Any adjustment of medicine (for example reducing the dose of a dopamine receptor agonist) should always be handled by a neurologist or the treating doctor. The local statistics quoted (such as the number of patients in Hong Kong and remarks by local experts) are estimates from local media reports and are not strict academic data. The sources are listed at the end of the article.

What is an impulse control disorder, and its four common forms

An impulse control disorder (ICD) means that the patient loses self-control over a certain type of behaviour and cannot stop, even when knowing it will have bad consequences. In people with Parkinson's disease, the four most common forms are as follows:

(The four prevalence figures above are all taken from the DOMINION study published by Weintraub et al. in 2010.) Besides these four main forms, some patients also show repetitive and aimless stubborn behaviours, such as taking apart and putting together objects or tidying things non-stop (called punding in medicine), which also belong to the spectrum of this condition (Weintraub et al., 2009).

How Parkinson's medicines cause impulse control disorders

To understand the cause, it is necessary to start from how Parkinson's disease is treated. Parkinson's disease comes from the degeneration of nerve cells in the brain that produce dopamine, so medicines that replace dopamine are commonly used in treatment, including a group called "dopamine receptor agonists" (such as pramipexole and ropinirole). The problem is that, besides improving motor symptoms, these medicines also stimulate the nerve circuits in the brain that deal with "reward and pleasure".

In terms of pharmacology, pramipexole and ropinirole have an especially high affinity for the D3 receptors in the brain (about 100 times and 25 times that for D2 receptors respectively), and D3 receptors are densely distributed in the mesolimbic system, which governs reward and motivation. When this circuit is over-stimulated, the patient loses the ability to inhibit behaviours that bring pleasure, such as gambling, shopping, sexual behaviour and eating (Zhang et al., 2021). This is therefore purely a physiological reaction of the brain driven by medicine, and has nothing to do with personality.

How common impulse control disorders are, and the research data

Many families think that "such an out-of-control and outrageous behaviour must be very rare". The research data show, however, that ICD is quite common among people with Parkinson's disease who take dopamine agonists:

It should be noted that DOMINION is a cross-sectional study (it counts the proportion affected at a single point in time), while the study published by Corvol et al. in 2018 is a prospective follow-up(it counts the proportion of people who develop symptoms cumulatively over several years), so the two sets of data cannot be compared directly. Both studies nevertheless confirm a fact: the longer the treatment and the higher the dose, the greater the risk of the side effect. Another authoritative review also pointed out that about 17% of people with Parkinson's disease taking dopamine receptor agonists develop an impulse control disorder (Voon et al., 2017).

High-risk medicines and patient groups at higher risk

Taking Parkinson's medicine does not necessarily cause the side effect above, but the following factors raise the risk markedly. If the family can recognise these high-risk factors, they can become alert early:

(For a review of the related risk factors, see Zhang et al., 2021. For the dependence on dose and time, see Corvol et al., 2018. The part on how doctors choose medicines is taken from a media interview with a local neurology expert and is an estimate from a local report.)

Department of Health information and analysis by local experts in Hong Kong

In Hong Kong, public education about this drug side effect is almost a blank, but there are two highly authoritative official and medical sources locally that have long stated it clearly:

Why families find it hard to notice early

The greatest harm that ICD does to a family often lies not in the out-of-control behaviour itself, but in the fact that the family usually has no idea that it is a drug side effect. As a result, many families find out that the whole matter was related to the medicine only after the patient has lost lifelong savings, built up heavy credit card debt, or the family relationship has broken down.

This blind spot has two main causes. First, the family simply does not know that Parkinson's medicines can cause this kind of side effect, so it is natural to blame the out-of-control behaviour on the patient "going bad" or "going bad in old age". Second, the patient often does not realise the behaviour is a problem, or hides it out of shame (especially behaviour involving gambling and sex). With these two factors together, the problem often only comes to light when it is already extremely serious.

Checklist of unusual behaviour in daily life

Families do not need a complicated professional assessment. They only need to watch for the kinds of unusual change below in daily life. If the patient shows any of the following, it is worth taking seriously and telling the treating doctor:

Clinically, healthcare staff can use a screening tool (such as the QUIP questionnaire, which covers gambling, sex, shopping, eating and other compulsive behaviours) to make systematic records, but screening is not the same as a formal diagnosis, and the final decision still has to be made by the doctor (Weintraub et al., 2009). For families, the most practical step is to help record what the unusual behaviour looks like and when it happens, and hand it to the doctor at the appointment.

Three steps to take when symptoms are suspected

Once ICD is suspected in a family member with the illness, doing the three things below right often matters more than any remedy afterwards:

1. 1
   Do not scold, and do not blame the person's character

   The family should remind themselves that this is a drug side effect and the patient's nature has not turned bad. Scolding only hurts feelings and makes the patient even less willing to speak up. The family can say calmly to the patient: "This may have something to do with your medicine, so let's tell the doctor together at the next appointment."
2. 2
   Tell the prescribing doctor as soon as possible

   Contact the neurologist or geriatrician who originally prescribed the medicine as soon as possible, and tell the doctor truthfully what unusual behaviour the patient has shown, and when and how often. ICD is a drug problem that can be managed, and the earlier the doctor is told, the smaller the effect on the family and its finances.
3. 3
   Do not stop the medicine or change the dose alone

   Stopping a dopamine agonist suddenly can cause a "withdrawal syndrome" and also makes motor symptoms worse (see the next section). How to reduce or switch medicines step by step must be decided by the doctor. What the family does is observe and report to the doctor, and never change medicines alone.

Directions for adjusting medicine and the medical evidence

The first-line approach to managing ICD clinically is for the doctor to assess and consider reducing the dose of, or stopping, the dopamine agonist. This direction has solid medical evidence behind it. The prospective study published by Corvol et al. in 2018 showed that, after the agonist was reduced or stopped under a doctor's guidance, ICD symptoms faded step by step within a year in about half of patients, which fully shows that the side effect is "caused by medicine and reversible with medicine".

As for other treatments, it has to be said frankly that the current medical evidence is not strong. For drug treatment (for example amantadine, SSRIs, antipsychotics or naltrexone), the related research evidence is insufficient (Zhang et al., 2021). The only non-drug approach currently supported by a randomised controlled trial is cognitive behavioural therapy (CBT). Note, however, that the study was only a small trial of 44 people. Although it showed that "CBT together with standard care" improved the severity of overall symptoms significantly more than "standard care alone" (p<0.001), the small sample and only moderate effect mean that more large studies are needed to verify it (Okai et al., 2013).

Hallucinations and delusions that may appear in the middle and late stages

Besides ICD, when Parkinson's disease reaches the middle and late stages, some patients may also have hallucinations (most often visual, for example seeing people or animals that are not there) and may even develop delusions(for example suspecting persecution, or that the spouse is unfaithful). These symptoms are likewise related to the dose of dopamine medicines, the progress of the disease and decline in cognitive function, and they do not mean "madness" or a problem of character.

The principle for dealing with them is the same as for ICD: the treating doctor must be told as soon as possible. The doctor usually looks first for triggers (such as a physical infection or a recent change of medicine), then adjusts the Parkinson's medicines step by step, and prescribes a safer medicine for control when necessary. Families should not manage this alone or struggle on by themselves.

Help that the home therapy team can give

On this subject, the role of NovaHealth is to give support, and not to prescribe or adjust medicines. For anything involving an adjustment of medicine, the team always advises the family to refer back to the treating doctor. Where a therapist can help is in practical support at the household level:

Where to get medical help, and community support organisations

In the following situations, the family should not wait until the next appointment. They should contact the treating doctor or seek help elsewhere at once: the family's finances or relationships have already been seriously harmed, the patient's sexual behaviour has become very distressing to the people around or threatens safety, the patient starts to have hallucinations or delusions, or the carer is close to physical and mental collapse. In Hong Kong, families can seek help through the following routes:

• Treating doctor / Hospital Authority outpatient clinic—The only correct route for adjusting medicines is the neurologist or geriatrician who originally prescribed them. If the patient is followed up at a public hospital, this can be done through the neurology and geriatric specialist outpatient clinics of the Hospital Authority.
• Hong Kong Movement Disorders Society (HKMDS)—Provides patient education information on Parkinson's disease and movement disorders, to help patients and families understand the illness and how it responds to medicines (a local organisation).
• The University of Hong Kong Jockey Club "柏動愛" Parkinson's care programme / Hong Kong Society for Rehabilitation—Provides community rehabilitation services, carer support and patient mutual-help groups (local organisations).

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