Abstract
Besides being better known for causing motor impairments, Parkinson's disease (PD) can also cause many nonmotor symptoms, like depression and anxiety, which can cause significant loss of life quality and may not respond to regular drugs treatment. In this review, we discuss the depression in PD, based on data from studies in humans and rodents. Depression frequency seems higher in PD patients than in general population, despite high variation in data due to diagnosis disparities. Development of depression in PD seems more likely to be caused by the nigrostriatal pathway degeneration than as a consequence of the awareness of disease prognostic, and it seems to be related to dopaminergic, noradrenergic, and serotoninergic synapses deficits. The dopaminergic role could be more significant, since it can modulate the release of the others, and its depletion is progressive, due to the degenerative feature of PD. Highly regarded in major depression, serotonin can be depleted in rats after nigrostriatal damage, but data from human patients are more conflicting. Animal studies can help in understanding the neurobiological mechanisms of depression in PD and the pursuit for more effective drugs for its treatment, but they lack the complexity of the disease progression, especially the nondopaminergic degeneration.
Highlights
Parkinson’s disease (PD) is a progressively debilitating neurologic disorder that affects about 6 million people around the world [1]
Incidence (4 to 75%) and prevalence (2.7 to 90%) of depression in PD patients in published studies vary substantially due to differences in depression definition or diagnostic criteria [22]
It is suggested that these toxins have different mechanisms of action, since MPTP causes a significant lesion only when infused at the substantia nigra pars compacta (SNc), a region rich in dopaminergic cell bodies, while 6-OHDA causes neuron degeneration when infused on cell bodies, axons, and even terminals [50,51,52,53]
Summary
Parkinson’s disease (PD) is a progressively debilitating neurologic disorder that affects about 6 million people around the world [1]. The striatal DA deficit interferes directly in the basal nuclei’s motor control circuitry, causing the most known PD symptoms: resting tremor, muscular rigidity, postural instability, and bradykinesia [3, 6, 7] These symptoms and the consequent PD diagnosis occur when about 50% of the dopaminergic neurons at the SNc are already degenerated and striatal dopamine has been reduced in 80%. Menza and coworkers reported depressive behavior in 92% of PD patients diagnosed with anxiety, as well as anxious behavior in 67% of PD depressed patients [17] Those symptoms are implicated as the highest causes of poor life quality among PD patients, affecting their daily activities and increasing incapability more severely than the motor symptoms, even when in their advanced stage [18,19,20]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
