A few days ago, I was in a coffee shop and overheard two sisters discussing their grandfather and his recent sexual behaviors. One said, “I was at the grocery with him yesterday and he was hitting on the cashier, who couldn’t have been more than 18 or 19. And it wasn’t just an old man being cute by flirting with a young girl. He was really hitting on her. I was embarrassed, and so was the girl. But Pop-Pop was clueless.” The other sister responded by saying, “It’s weird, isn’t it? Grandma told me she caught him looking at porn on the internet the other day, and she said it’s not the first time, either. Do you think this might be some weird symptom of his Parkinson’s Disease?”
If you are wondering, Parkinson’s Disease (PD) is a neurodegenerative disorder that affects dopamine producing neurons in the substantia nigra region of the brain. Essentially, dopamine producing cells die off, reducing dopamine levels in the brain. Because dopamine impacts movement (as well as pleasure and various other elements of the central nervous system), people with PD often experience physical tremors, usually starting in one or sometimes both hands. Other symptoms include slow movement, stiffness, and loss of balance.
Sexual dysfunction is another common issue. People with PD often experience a lack of sexual desire, erectile dysfunction, vaginal dryness, and difficulty reaching orgasm. Some of this may be psychological – perhaps related to the depression that often accompanies PD. But physical issues are also in play. For starters, dopamine, the production of which is significantly diminished with PD, is, as noted above, related to our experience of pleasure, potentially resulting in lowered sexual desire. Dopamine is also related to smooth motor function within our bodies, making sexual activity considerably more difficult and potentially less enjoyable.
Oddly, however, some people with PD become hypersexual rather than sexually bereft, as we see with Pop-Pop in the story above. Research tells us that this hypersexual behavior is related not to PD itself, but to medications used to treat it. In particular, therapies involving dopamine agonist drugs tend to be the culprit. (More on this later.)
So here we are with a (usually middle-aged or older) person suffering from PD, and that individual starts to behave sexually like a drunken teenager. Or a sex addict. They make inappropriate statements and advances, they spend all kinds of money in strip clubs and with prostitutes, they view porn for hours on end, and they masturbate to the point of physical injury. And these are people who were not in any way hypersexual prior to receiving certain PD meds. This means that they are not sex or porn addicts and should not be treated as such.
And it’s not just hypersexuality that PD patients experience. PD meds can induce a wide variety of impulsive and compulsive behaviors, such as pathological gambling, compulsive eating, and compulsive spending (Vilas, Pont-Sunyer & Tolosa, 2012). Research suggests that impulsive/compulsive behaviors of this sort are triggered in 1 out of 7 PD patients (Weiss & Marsh, 2012). Research also tells us that hypersexuality and other impulse control issues in PD patients can lead to significant financial loss and psychosocial morbidity for both patients and families (Vilas, Pont-Sunyer & Tolosa, 2012; Weiss & Marsh, 2012).
As stated above, the most common cause for this appears to be dopaminergic therapies that involve dopamine agonists. Dopamine agonists are drugs that activate dopamine receptors. They do not cause the production of dopamine, nor do they replace dopamine in the brain. They simply activate dopamine receptors, and the receptors then send signals throughout the brain as if they’ve just received a hit of dopamine.
Weiss and Marsh (2012) have also found that impulse control issues in PD patients tend to resolve if the dopamine agonist is withdrawn and PD symptoms are managed solely with the amino acid known as levodopa (more commonly referred to as L-Dopa). So it’s becoming more and more clear that dopamine agonists are the cause of hypersexuality, compulsive gambling, and other impulse control issues in PD patients. Unfortunately, the pathopsychological basis for this is, as yet, unknown, so short of removing the dopamine agonist drug (which often is working well with the PD symptoms), we are unable to mitigate the impulsivity/compulsivity side effects.
NOTE: The similarities we see between medication-induced hypersexuality in PD patients and sex addicts (and in fact all addicts) suggests there may be neurobiological commonalities that could help us better understand both PD and addiction, potentially developing more effective treatment methodologies for both (Politis et al, 2013). Of particular importance here is the concept of incentive salience, where the ‘wanting’ of the stimulus is more important than the actual reward from the stimulus. This factor arises with both PD (Berridge, 2007; Berridge, 2012) and sexual addiction (Mechelmans et al, 2014; Voon et al, 2014).
At this point, we do not know why some PD patients become hypersexual or otherwise impulsive or compulsive, while others on the same medications do not. It is possible that a propensity toward these behaviors in some way exists prior to the use of dopamine agonists, but at this point we cannot say for certain one way or the other. And if there are premorbid factors or biomarkers, we have no idea, as of now, what they are. If we did, we could refrain from using dopamine agonists in susceptible patients.
For now, it is important that clinicians who treat and work with PD patients, and also clinicians who treat and work with people who suffer from addiction (especially sex, gambling, and spending addiction) are aware of the potential side effects seen with dopamine agonists. PD clinicians should look for and ask about signs of impulsivity and compulsivity in their patients, and if those signs are spotted, a corresponding action (most likely the withdrawal of dopamine agonist drugs) should be taken. At the same time, addiction specialists should inquire about medications their clients are taking, and if dopamine agonists are part of the mix (for PD or, perhaps more likely, for restless leg syndrome), that should be looked at and addressed.
I do want to be clear here: I am not arguing against the use of dopamine agonists when it appears those drugs will help individuals with PD and similar disorders. I am simply saying that clinicians who work with PD and addiction should be aware of the potential side-effects of dopamine agonist drugs, and should monitor all patients on these drugs closely, knowing that behaviors that look impulsive/compulsive may be more about a medication than an individual’s psychological health.
Berridge, K. C. (2007). The debate over dopamine’s role in reward: The case for incentive salience. Psychopharmacology, 191(3), 391-431.
Berridge, K. C. (2012). From prediction error to incentive salience: Mesolimbic computation of reward motivation. European Journal of Neuroscience, 35(7), 1124-1143.
Mechelmans, D. J., Irvine, M., Banca, P., Porter, L., Mitchell, S., Mole, T. B., … & Voon, V. (2014). Enhanced attentional bias towards sexually explicit cues in individuals with and without compulsive sexual behaviours. PloS one, 9(8), e105476.
Politis, M., Loane, C., Wu, K., O’Sullivan, S. S., Woodhead, Z., Kiferle, L., … & Piccini, P. (2013). Neural response to visual sexual cues in dopamine treatment-linked hypersexuality in Parkinson’s disease. Brain, 136(2), 400-411.
Vilas, D., Pont-Sunyer, C., & Tolosa, E. (2012). Impulse control disorders in Parkinson’s Disease. Parkinsonism & related disorders, 18, S80-S84.
Voon, V., Mole, T. B., Banca, P., Porter, L., Morris, L., Mitchell, S., … & Irvine, M. (2014). Neural correlates of sexual cue reactivity in individuals with and without compulsive sexual behaviours. PloS one, 9(7), e102419.
Weiss, H. D., & Marsh, L. (2012). Impulse control disorders and compulsive behaviors associated with dopaminergic therapies in Parkinson disease. Neurology: Clinical Practice, 2(4), 267-274.