Sudden, extreme changes in emotion. Mood swings are common in Parkinson’s disease and are often among the earliest symptoms, although this becomes clear retrospectively. Parkinson’s disease develops when so many dopaminergic neurons die that there is no longer an adequate supply of dopamine, the neurotrans-mitter largely responsible for brain functions related to movement. Because dopamine is present in other parts of the brain that regulate mood, emotion, and cognitive function, many researchers believe there is also dopaminergic neuron loss in those areas as well, although not as pronounced as in the basal ganglia (the part of the brain that regulates movement). This, some researchers believe, accounts for mood swings in people with Parkinson’s, as well as related symptoms such as DEPRESSION, MEMORY LOSS, and COGNITIVE DYSFUNCTION.
Many people with Parkinson’s disease find that mood swings and related symptoms such as depression improve during an on-state, when anti-parkinson’s medications are most effectively controlling neuromuscular symptoms or change when their medication regimens change, although clinical research trials studying such correlations provide conflicting results. Mood swings are also symptoms of other conditions that may or may not be related to Parkinson’s disease, such as Alzheimer’s disease, or that occur as side effects of various anti-Parkinson’s medications.