According to a 2002 review in "American Family Physician," depression is the second-most common chronic disorder seen by primary care physicians, and major depression affects more than 10 percent of Americans. Medications are often prescribed for treating depression. Most of these agents are designed to increase the levels of important chemicals, such as dopamine, in your brain.
Neurotransmitters are Chemical Messengers
Your nervous system is a complex array of nerve fibers that, like electrical wiring, relay impulses from one site in your body to another. However, unlike electrical wiring, your nerves aren't continuous. Each neuron is separated from its neighbor by a microscopic space called a synapse. As impulses reach the end of a neuron, chemical messengers called neurotransmitters are released into the synapse, where they stimulate receptors on the adjoining neuron. This relays the impulse onward. In many cases, the neurotransmitters -- serotonin, epinephrine, norepinephrine, dopamine and others -- are then reabsorbed by the neurons. Low levels of neurotransmitters, including dopamine, are believed to contribute to depression.
Dopamine Exerts Wide-Ranging Effects
Your brain is richly endowed with receptors that respond to dopamine. In fact, according to the American College of Neuropsychopharmacology, at least five biochemically different dopamine receptors are scattered throughout your central nervous system, with many vital centers containing several different types of dopamine receptors. Stimulation of these receptors influences your mood, emotions, movement, motivation, memory, cognitive ability and even hormonal function.
Dopamine in Depression
Insufficient dopamine production has been implicated as a cause for depression. A 2010 "Frontiers in Neuroscience" review contends that all antidepressant treatments eventually trigger a dopamine-dependent pathway in order to exert their therapeutic effects. Furthermore, the usefulness of a given treatment is determined by how effectively it stimulates dopamine receptors. However, due to the complex interplay among neurons that produce serotonin, epinephrine, norepinephrine, dopamine and other neurotransmitters, depression is often treated with medications that affect "upstream" neurotransmitters but have fewer side effects than classical agents, which mainly addressed dopamine levels.
Considerations
Low dopamine levels are believed to play a major role in the genesis and persistence of depression. Most antidepressant medications either affect dopamine levels directly, or they indirectly influence dopamine activity by affecting interconnected neurons that produce alternative neurotransmitters. However, the exact mechanisms that contribute to depression are still poorly understood, and individual responses to antidepressant treatments vary considerably. If you suffer from depression, ask your doctor about the best treatment for you.
References
- "American Family Physician"; Screening for Depression Across the Lifespan: A Review of Measures for Use in Primary Care Settings; L.K. Sharp, M.S. Lipsky; September 2002
- American College of Neuropsychopharmacology: Molecular Biology of the Dopamine Receptor Subtypes; O. Civelli; 2000
- "Frontiers in Neuroscience"; A New Strategy for Antidepressant Prescription; F. Lavergne, T.M. Jay; November 2010
- "Therapie"; Mechanism of Action of Antidepressants and Therapeutic Perspectives; M. Bourin, et al.; July-August 2002
