While many factors can cause humans to feel sad for variable periods of time, true depression is a psychiatric symptom that has clear chemical origins. Research on depression and in the field of neuropsychology has revealed that low levels of certain neurotransmitters lead to symptoms of depression. Further, chemicals that raise levels of these neurotransmitters can relieve symptoms.
History
The first of the neurotransmitters to be linked to depression was serotonin, which is sometimes called the "happy neurotransmitter." Serotonin has many effects on the brain, one of which is to promote feelings of relaxation and well being. Serotonin deficiencies lead to depression and anxiety, explain Drs. Reginald Garrett and Charles Grisham in their book, "Biochemistry." Early attempts to treat depression involved drugs designed to prevent the body from breaking down serotonin, called MAOI drugs.
Significance
The chemicals involved in producing depression, scientists have since found, are much more varied and variable--serotonin is not the sole cause of depression, nor is it the cause in every case. Researchers have identified norepinephrine, a brain chemical very similar in structure to epinephrine, as an additional culprit in producing chemical depression. In a 2004 article published in "Fundamentals of Clinical Pharmacology," researchers examined the role of dopamine, another neurotransmitter, in depression, and found that it also caused symptoms if concentrations were low.
Effects
Low levels of neurotransmitters including serotonin, dopamine, and norepinephrine leads to serious and persistent symptoms of depression. These include loss of interest or pleasure in life, low sex drive, feelings of despair, and chronic fatigue, explains MayoClinic.com. While normal human sorrow strikes from time to time, depression is continuous, isn't related to life events, and in serious cases, can lead individuals to think about dying or committing suicide. These effects are all products of faulty chemical signals in the brain sent by low levels of neurotransmitters.
Treatment
Thankfully for depression sufferers, since depression has a chemical basis, there are also chemicals that can have positive effects upon depression. These are the depression pharmaceutical drugs, and include the older MAOI drugs, as well as newer generation drugs called SSRIs. Like MAOIs, SSRIs, including Prozac, effect only serotonin. However, serotonin levels are so key to depression symptoms in so many cases that many individuals do quite well on serotonin-adjusting drugs, notes Dr. Neil Carlson in his book, "Fundamentals of Physiological Psychology."
Expert Insight
Some cases of depression require more than just adjustment of serotonin. MayoClinic.com notes that a newer drug marketed under the brand name Wellbutrin helps to adjust levels of dopamine and norepinephrine as well as serotonin, making it the only drug currently available on the market to do so. For individuals who don't respond well to serotonin drugs, Wellbutrin may offer relief from symptoms. Many antidepressant drugs increase blood pressure, so all individuals on antidepressants require physician monitoring.
References
- "Biochemistry"; Reginald Garrett, Ph.D. and Charles Grisham, Ph.D.; 2007
- "Fundamentals of Clinical Pharmacology"; Dopamine, depression and antidepressants; E. Dailly et al.; December 2004
- MayoClinic.com: Depression
- "Foundations of Physiological Psychology"; Neil Carlson, Ph.D.; 2004
- MayoClinic.com: NDRI Drugs
