Dopamine is a neurotransmitter that plays a large and very important role in the body's cardiovascular, renal, hormonal and central nervous systems. Dopamine levels heavily influence motor function and brain thinking, and as such low levels have been linked to both mental and physical health disorders or diseases.
Motor Control Loss and Parkinsons Disease
Low levels of dopamine in the brain can produce motor-control problems, while very low levels can lead to Parkinson's Disease, according to Clinical Psychologist Dr. Joseph Carver in his article "Dopamine: Parkinson's Disease and ADHD to Smoking and Paranoia" which appears in eNotAlone.com. The symptoms of Parkinson's disease, which Dr. Carver attributes to low dopamine levels, include muscle rigidity and stiffness, loss of balance and coordination, tremors, and even slow, impaired speech.
Impaired Focus and ADHD
Low levels of dopamine can affect the portions of the brain that impact thinking, impairing the ability to concentrate and focus, according to Dr. Carver in his article. Perhaps not surprisingly, Dr. Carver links low levels of dopamine with attention-deficit hyperactivity disorder (ADHD), the primary symptom of which is difficulty focusing and concentrating.
Dopamine has been linked to depression, according to Dr. Donald S. Robinson in an article titled "The Role of Dopamine and Norepinephrine in Depression" which appeared a 2007 edition of Primary Psychiatry. His article points to evidence suggesting that "depressed patients have reduced levels of homovanillic acid (HVA), the major metabolite of dopamine in the central nervous system." His article points out that understanding the relationship between HVA levels and depression will have major implications in the treatment of the condition.