Tuesday, May 11, 2010

Parkinson's Medications and Impulsive Behavior

There have now been several studies documenting an increase in impulse control disorders such as compulsive gambling, sexuality, shopping and other similar behaviors in people taking medications for Parkinson's Disease. These studies demonstrate that the brain, which regulates thinking, feeling and behaving, can become disordered in certain ways. In this case it is from a medication to treat Parkinson's Disease. These medications increase dopamine release, thus they add evidence to the dopamine hypothesis of impulse control disorders, including addiction to drugs. What I find interesting about them is that these were not previous drug or sex addicts or compulsive gamblers. But once their dopamine balance became dysregulated, their behavior became dysregulated. Thus, if our brain is dysregulated in certain ways, it constrains our ability to exercise choice or will. This complicates questions about responsibility, moral blameworthiness, and criminal liability. But what is becoming ever more clear as I work with many patients again is that there is a dysregulation of the ability to control behavior. The ethical and political arenas will simply have to deal with that. Here is a recent study:

Impulse Control Disorders in Parkinson Disease
A Cross-Sectional Study of 3090 Patients
Daniel Weintraub, MDJuergen Koester, PhDMarc N. Potenza, MD, PhDAndrew D. Siderowf, MD, MSCEMark Stacy, MDValerie Voon, MD;Jacqueline Whetteckey, MDGlen R. Wunderlich, PhDAnthony E. Lang, MD, FRCPC 
Arch Neurol. 2010;67(5):589-595.
Context  An association between dopamine-replacement therapies and impulse control disorders (ICDs) in Parkinson disease (PD) has been suggested in preliminary studies.
Objectives  To ascertain point prevalence estimates of 4 ICDs in PD and examine their associations with dopamine-replacement therapies and other clinical characteristics.
Design  Cross-sectional study using an a priori established sampling procedure for subject recruitment and raters blinded to PD medication status.
Patients  Three thousand ninety patients with treated idiopathic PD receiving routine clinical care at 46 movement disorder centers in the United States and Canada.
Main Outcome Measures  The Massachusetts Gambling Screen score for current problem/pathological gambling, the Minnesota Impulsive Disorders Interview score for compulsive sexual behavior and buying, and Diagnostic and Statistical Manual of Mental Disorders research criteria for binge-eating disorder.
Results  An ICD was identified in 13.6% of patients (gambling in 5.0%, compulsive sexual behavior in 3.5%, compulsive buying in 5.7%, and binge-eating disorder in 4.3%), and 3.9% had 2 or more ICDs. Impulse control disorders were more common in patients treated with a dopamine agonist than in patients not taking a dopamine agonist (17.1% vs 6.9%; odds ratio [OR], 2.72; 95% confidence interval [CI], 2.08-3.54; P < .001). Impulse control disorder frequency was similar for pramipexole and ropinirole (17.7% vs 15.5%; OR, 1.22; 95% CI, 0.94-1.57; P = .14). Additional variables independently associated with ICDs were levodopa use, living in the United States, younger age, being unmarried, current cigarette smoking, and a family history of gambling problems.
Conclusions  Dopamine agonist treatment in PD is associated with 2- to 3.5-fold increased odds of having an ICD. This association represents a drug class relationship across ICDs. The association of other demographic and clinical variables with ICDs suggests a complex relationship that requires additional investigation to optimize prevention and treatment strategies.

1 comment:

  1. Marijuana can be very addictive. It is not because of dopamine. These studies to support the links of addiction to dopamine do not really tell us anything that significant. You could do a study on people that used marijuana and link the effects of the drug on binge eating behavior. Is that a real important link? Some people take anti-depressants for depression. For some, it is effective and explained by the reuptake of serotonin. But, for others, it makes them more depressed, so serotonin in these individuals is not an explanation. What if you did a study on people that became suicidal taking anti-depressants. Would the study conclude that the use of reuptake drugs is linked to suicide so don't take them? People are different. Lab studies on animals are of limited value, because animals don't subjectively make choices. The person taking PD drugs that develops an impulse control problem still has some control or they would never decide to gamble in the first place. Dopamine depletion does not make some one into a robot. This is the way these studies always sound. Am I missing something here?

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