Parkinson’s disease (PD) is a disease that affects movement and motor capabilities. PD also has a variety of non-motor symptoms, of which anxiety and depression are especially common. These psychiatric disorders are referred to by healthcare professionals as affective, or mood, disorders. It is estimated that 25-75% of patients with PD will experience significant symptoms of anxiety or depression at some point during their illness [1, 2].
Depression is a common mental health issue. The National Health and Nutrition Examination Survey, 2009–2012 reported that 7.6% of Americans aged 12 and over, experienced moderate or severe depressive symptoms, when polled about mood during the last two weeks .
Depression can be more difficult to identify in patients with PD. Lack of energy or inability to accomplish daily activities may be attributed erroneously to the motor symptoms of PD, rather than to a depressive episode. Some of the common signs and symptoms of depression are:
Persistent sad, anxious, or “empty” mood
Feelings of hopelessness or pessimism
Feelings of purposelessness
Loss of interest or pleasure in hobbies and activities
Decreased energy or fatigue
Excessive slowness in daily activities
Difficulty in concentrating, remembering, or making decisions
Difficulty in falling asleep, or early morning awakening
Appetite and/or weight changes 
Doctors used to think that depression in patients with PD patients was an emotional response to the diagnosis of their disease. A newer theory is that the disease itself is the cause of these mood issues [5-7].
Depression is a result of chemical imbalances in the brain . There have been significant successes in mental health treatment using drugs such as fluoxetine (Prozac) or bupropion (Wellbutrin). These drugs are classified as selective serotonin reuptake inhibitors (SSRIs), which means that they block the reabsorption of serotonin—a chemical in the brain that is linked to mood stability. By allowing this neurochemical to remain in the brain for longer, the mood benefits of these drugs are sustained.
Anxiety—like depression—is common in PD patients [5, 6, 9]. Along with SSRIs, which can produce anti-anxiety benefits, another class of drugs exists for treating generalized anxiety disorders and panic attacks: serotonin-norepinephrine reuptake inhibitors (SNRIs). These drugs block the reabsorption of these two neurotransmitters and should be used in preference to benzodiazepines, which have more side effects and can be habit-forming. SSRIs and SNRIs stabilize mood, and in many cases can provide satisfactory relief from depression and anxiety. Psychological counselling, in addition to a drug therapy regimen, is optimal .
It may take up to three months or so after initiation of an anti-depressant before there is a reduction of symptoms [10, 11]. Patients must allow time for the medication to work and for most patients, treatment should continue for at least a year after it begins to help.
In addition to medication, exercise is effective [12-14] in the treatment of depression. Outdoor exercise is particularly helpful as sunlight helps stimulate the brain to produce serotonin. Social interaction is also beneficial for mood and stimulates the brain .
Patients may not recognize that they are depressed. It is helpful for a spouse, partner, or close friend to accompany patients to follow-up appointments, as they can help answer questions on mood changes and level of social activity.
For patients taking carbidopa/levodopa (Sinemet), complications can arise after months or years of treatment. There may be response fluctuations, either “wearing off” effect or “on/off” periods. A “wearing off” effect is when a patient is aware of a loss of symptomatic benefit of Sinemet before the next scheduled dose. “On/off” periods are response fluctuations marked by rapidly cycling response changes—shifting between normal, under-medicated, and over-medicated states without any relationship to the timing of doses. Depression and anxiety may occur in patients with these complications, particularly when a patient is in an “off” stage. While treating the on/off motor phenomena can be difficult, the medical treatment of depression and anxiety should be the same as in any patient with a similar mood complaint.
Patients with PD should see a neurologist regularly so that their symptoms are managed optimally. Symptoms of depression and anxiety —similar to motor symptoms— should also be discussed.
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