Impulse Control Disorders Common in Parkinson's Disease
October 26, 2006 — Two new studies examine the problematic disorders of
impulse control — including repetitive behaviors, pathological gambling, and
hypersexuality — seen in patients with Parkinson's disease (PD), particularly
those on dopamine agonists.
In these reviews, the prevalence of these behaviors was between 6% and 13%,
depending on which drug the patients were taking, "so it's not uncommon,"
Kevin J. Black, MD, from the Washington University School of Medicine, in St.
Louis, Missouri, coauthor of an editorial accompanying the papers, told
Medscape. "There's very little real scientific data about it – including
which patients are more susceptible — so this is really the beginning of the
research in a way."
The reports appeared in the October 10 issue of Neurology.
Establishing Prevalence
While hypersexuality has been described in relation to levodopa therapy since
the 1970s, when the drug was first introduced, in the past 10 to 15 years
other complex, repetitive behaviors have been described, particularly in
relation to newer dopamine agonist drugs, Dr. Black noted. These fall into 2
categories: disinhibited behaviors, things that patients "have had some
interest in but suddenly [it] becomes a passion or addiction, like gambling,
Internet card-playing, or various kinds of sexual activity — even shopping."
The other type of behavior has been called punding, a specific repetitive
behavior such as, for example, emptying a dresser drawer, then replacing all
the items, and emptying it again.
"It's been interesting in the past several years, because it's been recognized
to be maybe a bit more frequent than we previously expected, particularly
because it's associated with significant psychosocial dysfunction and can be
quite hidden as behaviors," Valerie Voon, MD, from the National Institute of
Neurological Disorders and Stroke, in Bethesda, Maryland, first author on 1
of the current reports, told Medscape. "The reason we got interested in these
behaviors is there weren’t any good studies that systematically assessed the
prevalence rates."
In their study, Dr. Voon and colleagues at the Toronto Western Hospital, in
Toronto, Ontario, surveyed 297 patients with PD using systematic screens and
rigorous definitional criteria with the aim of establishing the prevalence of
hypersexuality and compulsive gambling specifically, as well as any
association with medication in a case-control design.
They found that the lifetime prevalence of pathologic hypersexuality was 2.4%.
Compulsive shopping prevalence was 0.7%. Combined with their previously
reported data on pathologic gambling, where the lifetime prevalence was 3.4%
(Neurology. 2006;66:1750-1752), the lifetime prevalence of any of these
behaviors was 6.1%.
This increased to 13.7% among patients who were on any type of dopamine
agonist, a relationship that has been reported previously by this and other
groups. For example, in their own previous paper on pathologic gambling,
gambling was associated with dopamine agonists as a class effect, without any
association with dose or agonist type, Dr. Voon noted.
She added that in that previous paper, they'd found patients who were gambling
had lost a mean of $100,000, and 40% of patients with this disorder had
experienced threatened or actual marital dissolution, "so these are very
disruptive behaviors," she said.
"We are now generally warning anyone in whom we're about to start a dopamine
agonist about these behaviors as a potential side effect, along with other
side effects such as fatigue and sleep disorder, and will also screen for
these disorders on routine follow-up," Dr. Voon told Medscape.
Establishing risk factors for these behaviors could be potentially useful,
allowing more vigilant follow-up or consideration of alternative therapies to
dopamine agonists in susceptible individuals, she added.
Clinical Features and Impulse Control Disorders
In a second paper in the same issue of Neurology, Gregory Pontone, MD, from
Johns Hopkins University School of Medicine, in Baltimore, Maryland, and
colleagues looked at clinical features associated with impulse control
disorders, including hypersexuality and pathologic gambling or shopping, in a
group of PD patients.
The hope, the authors noted, was that delineating these factors might improve
detection of these "devastating complications of antiparkinsonian treatment."
They studied 66 men and 34 women with idiopathic PD who had been recruited for
a longitudinal study looking at work- and social-related disability in PD.
Subjects were 65 years of age or younger, were nondemented, and had no
history of current substance abuse or psychotic disorder.
Of 66 men and 34 women who underwent psychiatric interview, 6 men and 3 women
were found to have 1 of several impulse control disorders, including
pathological gambling or shopping or hypersexuality, for an overall
prevalence of 9%.
The presence of these disorders was associated again with the use dopamine
agonists, but also with depressed mood, disinhibition, irritability, and
appetite disturbance.
A Silver Lining?
In their editorial, Dr. Black and coauthor Joseph H. Friedman, MD, from Brown
University Medical School in Providence, Rhode Island, write that the 2 new
papers by Voon and colleagues and Pontone and colleagues "add important
clinical information" about these disorders, but questions remain.
Among these is whether dopamine agonists are associated with these behaviors
in other disorders where they are used, such as restless legs syndrome, they
point out. Further, it's not clear why other impulsive behaviors such as
pyromania are not seen or at least have not yet been recognized in patients
with PD.
Finally, they note, "These observations provide a dramatic illustration that
problem behaviors, often linked to moral turpitude, may be biochemical in
origin and not the result of poor upbringing or deficiencies in moral fiber."
If dopamine agonists cause de novo problem gambling, for example, it may be
possible to devise treatments for the more common variety of gambler, they
speculate. However, already, a trial using a dopamine antagonist in patients
with non-PD related pathologic gambling showed no effect of treatment.
"Time will tell what we learn from these unfortunate experiences, but it is
hard to imagine that there will not be a silver lining, at some point, to
this cloud of problematic side effects," Drs. Black and Friedman conclude.
Neurol. 2006;67:1254-1257, 1258-1261, 1118-1119.
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