Patient description: A 57-year old farmer was diagnosed with Parkinson's disease a year ago. He experiences slowness of movement and tremors. His past medical history is significant for hypertension and hypercholesterolemia. He lives with his wife. They have three children. He used to be active with planting and taking care of their farm animals before his diagnosis. The patient complains of shaking and slow movement. He had difficulty entering through a door, as he was frozen and needed guidance to step in. His handwriting is getting smaller. He is on Levodopa and Trihexyphenidyl. He stated his medications help with shaking and slow movement. But he still has difficulty initiating movements, stiffness and slowness in general. He is an alert and cooperative man who doesn't have any signs of dementia. He doesn't smoke or use any illicit drugs.

Clinical trial eligibility criteria: eligible ages (years): 25.0-40.0,  Traumatic Brain Injury Neurobehavioral Manifestation Sleep Disorder Fatigue Are 25 to 40 years of age Are active duty service members or veterans May be NIH employees/staff who are either active duty service members or veterans; except for those who are employed by NINR or subordinates, relatives, and/or co-workers of NINR employees/staff Have sustained at least 1 TBI, >= 6 months and <= 5 years since their most recent TBI, which includes any self-reported loss of consciousness (LOC) established by the OSU during the pre-screening phone call Are able to provide their own consent Are able to understand the protocol, as shown by scoring a 6 out of 6 on a consent quiz  Currently receiving treatment for a medical illness or recent injury that precludes protocol participation, may interfere with study participation, and/or should be treated/stabilized prior to study participation for safety reasons (e.g., cancer, recent fracture(s) requiring therapy and/or pain medication, severe infection). Individuals with stable medical conditions such as hypertension that are controlled by medication will be included Current physical health status will be assessed by self-report, history and physical exam by a credentialed physician or nurse practitioner, and standard laboratory tests Current unstable endocrine disorder (e.g., uncontrolled diabetes). Unstable endocrine disorders require treatment to ensure health and safety of the patient before participation is possible. Individuals with stable endocrine disorders (e.g., controlled diabetes) may participate in the protocol but they will be excluded from the hydrocortisone stimulation test. This will be assessed by self-report during the history and physical exam and by standard laboratory tests Have a major medical illness that is associated with fatigue (e.g., chronic fatigue [diagnosed prior to their TBI or less than 6 months following TBI], multiple sclerosis, or cancer). This will ensure that symptoms of fatigue are as a result of TBI and not another co-morbid illness. This will be assessed by self-report Currently consuming any of the following sleep modifying medications: benzodiazepines; benzodiazepine receptor agonists; opiates; or sedatives. These medications will directly affect the results of the PSG and actigraphy analysis, as such participants currently taking these medications will be excluded. This will be assessed by self-report Currently using the sleep modifying medications melatonin and/or Benadryl greater than 2 times per week and/or unable or unwilling refrain from using them during protocol participation. These medications will directly affect the results of the PSG and actigraphy analysis, as such participants who are unwilling/unable to refrain from using these medications will be excluded. This will be assessed by self-report Current psychiatric condition for which immediate treatment is required to prevent harm to self or others such as active suicidality or active manic phase in someone who has bi-polar disorder. This is to ensure patient safety and care. This will be assessed by self-report and as part of the history and physical exam Are pregnant. Pregnancy is associated with increased fatigue and sleep disturbances, as such this condition will affect the outcomes of this analysis.his will be assessed by self-report. This will also be assessed on visit 2 by a urine pregnancy test. Individuals who are nursing are eligible but will not participate in the hydrocortisone stimulation test Received a diagnosis of severe obstructive sleep apnea (OSA) and/or current reliance on continuous positive airway pressure (CPAP) therapy to aid sleep. Severe OSA and CPAP use will directly affect the result s of this study, as such these participants will be excluded. This will be assessed by self-report. **Participant may be able to participate in the protocol but will not be able to have an MRI if they have any of the following Metal in the body such as pacemakers, stimulators, pumps, aneurysm clips, metallic prostheses, artificial heart valves, cochlear implants or shrapnel fragments, or if they are a welder or metal worker