Impulse Control Disorders in Parkinson's Disease
by Greg Pontone, MD
Impulse control disorders (ICDs) are behavioral disturbances in which a person fails to resist the drive to behave in ways that result in distress or impaired social and occupational functioning. In Parkinson's disease (PD), ICDs most commonly include pathological gambling, excessive spending and hypersexuality. It is not uncommon for individuals to have more than one ICD concurrently or an ICD other than those listed above, i.e. impulsive eating, skin picking. ICDs involve a spectrum of behaviors and this concept can act as a guide to screen for related disorders within this category.
The prevalence of ICDs, as a group, in PD is unknown. One recent study conducted at Johns Hopkins Hospital found that ICDs were present in 9% of patients in a research study involving PD patients younger than 65. Studies looking at rates of specific ICDs in clinic populations found that pathological gambling and hypersexuality, individually, affected 2-5% of patients.
There are a number of similarities among the different types of ICDs. First, it is important to note that gambling, sex and shopping, the most frequently reported ICDs, are all within the normal repertoire of human behaviors. It is the unusual extent and frequency of ICD behaviors that make them maladaptive and detrimental. Often, the ICD behaviors are continued despite the knowledge that performing them will lead to bad outcomes and adverse consequences. This point helps differentiate ICDs as a disorder of behavior as opposed to a disorder of cognition. With a disorder of cognition, a person may be unable to tell right from wrong. By contrast, in a behavioral disorder, the person can distinguish right from wrong but is unable to conform his or her actions to those standards. In the example of pathological gambling, the individual knows that spending their retirement savings on gambling is wrong, but is unable to resist the urge to do so.
Psychiatrists define pathological gambling as persistent and recurrent maladaptive gambling behavior that the patient has made repeated unsuccessful efforts to control. Often, affected persons will lie to family members or others to conceal the extent of involvement with gambling. It is not uncommon for an otherwise law abiding person to commit illegal acts such as forgery, fraud and even theft to support the behavior.
Hypersexual behaviors vary from person to person, but represent a deviation from the individual's usual sexual activity in frequency, intensity or context. Hypersexuality can start as intrusive thoughts or urges and trend into inappropriate remarks or acts. Some patients may begin to use pornography, patronize prostitutes, or develop paraphilias. Paraphilias involve recurrent, intense sexually arousing fantasies, urges or behaviors, including activities such as sado-masochism, exhibitionism or frotteurism (the practice of achieving sexual stimulation or orgasm by touching and rubbing against a person without the person's consent and usually in a public place). The altered sexual activity can occur within an established context (e.g., increased demand for sex with one's spouse, perhaps involving new types of sexual behaviors) or it may devolve into indiscriminate sexual activity in random contexts.
Excessive shopping and other impulse control disorders (i.e. skin picking) have also been described in patients with PD and share common features of being behaviors that are difficult to resist and distressing. Examples of excessive shopping might include the purchase of 15 art-deco lamps for a modest two bedroom house or clothes that one never wears or shopping for mundane items with abnormal frequency (grossly beyond what is needed). One patient frequently purchased items at a local warehouse store, e.g., 25 fire extinguishers, and would later justify such purchases by saying they were going to be used as employee gifts.
Impulsive behaviors that occur in patients with PD can be difficult to distinguish from other psychiatric disturbances that can also occur in PD. Manic or hypomanic disturbances are characterized by persistently elevated, grandiose or irritable mood states and can involve impulsive over-activity, including inappropriate spending, sexual activity, or gambling. However, with ICDs, the overactive behavior is highly focused and driven. In general, ICDs in PD patients tend to be distinct from manic or hypomanic states. ICDs are also not part of an obsessive-compulsive disorder, in which repetitive unwanted thoughts (obsessions) compel a person to perform ritualistic behaviors (compulsions) to reduce anxiety. Instead, impulsive behaviors are often motivated by pleasure, gratification or some other reward. In humans, the brain regions involved in reward are believed to be largely controlled by dopamine, the same neurotransmitter involved in the movement centers of the brain. Therefore the alteration of dopamine levels due to PD and the medications used to treat PD may contribute to a disturbance in the reward system. Medical literature supports a strong association between impulse control disorders and anti-parkinson's medication, especially the dopamine agonists. However, the relationship is far from causal, because the vast majority, >90%, of patients do not develop ICDs even when taking very high doses of the medication for long periods. Genetic differences in dopamine receptors and metabolism most likely play a role in determining which patients are at greatest risk.
So far, there is no clear way to predict which patients will develop ICDs. In general, ICDs appear to be more likely to develop in younger patients. Symptoms of depression, irritability, and appetite disturbances may be associated with the presence of the behaviors. It is probably a good idea for physicians to ask all patients about ICDs, but the presence of such symptoms should raise inquiry about ICDs. It is important for caregivers to communicate these symptoms to the physician if the patient does not want to reveal that these behaviors are problematic. Like many unwanted side effects of medications, ICDs often start when dopaminergic medications are increased or when a second dopaminergic drug is added. Because of that, it is important for the physician to continue to ask for a patient and/or caregiver report about ICDs at follow-up visits, especially after dose changes. The recognition by clinicians and patients that there is a relationship between PD, anti-parkinson's medications, and ICDs will help improve detection of these behaviors, which are often hidden out of shame or unrecognized because the association with PD was not made.
The treatment of impulse control disorders in PD is challenging because the medications that are needed to treat the movement disorder aspect of PD are often the precipitating agents of ICDs. Stopping anti-parkinson's medications altogether in order to treat an ICD is not practical. However, stopping or reducing the dose of the suspected agent often helps. Usually, when a dopamine agonist is suspected of contributing to an ICD, the patient can be switched to levodopa. If the agonist was added to levodopa to improve movement, options include using a higher dose of levodopa or using other medicines, such as entacapone, to prolong the effectiveness of the levodopa dose. Many patients report rapid cessation of ICD symptoms and behaviors after they stop dopamine agonists. However, if motor symptoms are not adequately controlled, patients may be tempted to resume the dopamine agonist, without informing others, and the behaviors can return. In some cases, it is unclear whether the offending agent, most often a dopamine agonist in our experience, is mostly giving patients an enhanced sense of well-being (the reward) or if the agonist actually provides a greater sense of control over motor symptoms. When stopping the offending antiparkinson's medication is not effective or not an option, we have frequently added low dose quetiapine, an antipsychotic, and this often has a clear effect on helping the patient resist impulses. Unfortunately, not every patient can tolerate quetiapine, which has the potential to worsen motor function in PD.
Regardless of the pharmacologic intervention used to treat ICDs, behavioral measures are also an important part of management. Behavioral measures are especially important because they can prevent some of the consequences of such behaviors. Behavioral interventions include taking away credit and bank cards, and limiting account access in the case of gambling. Restricting use of the Internet and video player can help in some cases for hypersexuality. For some ICDs 12-step gambling groups can also be helpful.
Once an impulsive behavior is recognized, the most important and first step a patient or caregiver should take is to inform the patient's physician. Stopping or changing medication doses without guidance can produce unwanted side effects in other aspects of functioning. It is also important to confirm that the impulsive behaviors are not occurring in the context of an affective disorder (i.e. bipolar disorder) which if left untreated could lead to further impairment of functioning.
Dr. Pontone is a psychiatrist at Johns Hopkins University School of Medicine where he is a clinical research fellow in Geriatric Psychiatry and Movement Disorders. Dr. Pontone's research focuses on the neuropsychiatric aspects of PD and other movement disorders.