Biological Causes Of Depression Essay

Depression is a complicated process as it seems be the effect of more than one process. There are many theories surrounding the biological side of depression, however the two prominent ones have developed many studies and encouraged many debates for its cause. The monoamine hypothesis and the neurotropic hypothesis are both different theories concerning the cause of depression, however both holds strong evidence, and when studied further, leads to the possibility of overlap and linkage between the two.
The depletion of the levels of serotonin, norepinephrine and dopamine in the central nervous system is a theory used to explain depression, called the monoamine hypothesis of depression (Delgado, P. L., 2000). This came about with the early development

LSD was found to block serotonin receptors and judging by the well known effects of serotonin, it was suspected that it was involved in depression’s symptoms. The most profound discovery however, came from the 1950s, where reserpine was used to treat high blood pressure, however caused depression as an unwanted side effect. Further studies showed that it caused a depletion of serotonin and noradrenaline, which are components of monoamines in the brain (Iversen, L., 2005).
One study on this hypothesis included trying to confirm that monoamines were in fact the cause of depression, included manipulating monoamines in an attempt to change a person’s symptoms. Delgado, P. L. (2000), presented a study that reduced levels of monoamines in different subjects. The prediction was that if there was a deficiency, there will be significant changes in the subject’s symptoms. Manipulation of serotonin was given through a tryptophan-free drink, as serotonin manufacture was dependent on the availability of tryptophan, reducing their levels would also deplete them of serotonin. For norepinephrine and dopamine, subjects were given an administration of AMPT, which inhibits

Asberg, M., Träskman, L., & Thoren, P. (1976) took 68 depressed patients with no history of drug abuse, schizophrenia, or brain damage, and examined their cerebral spinal fluid by drawing them out and centrifuging them. They grouped serotonin levels into low and high, and found that more patients in the low group than in the high group have tried to commit suicide, with two patients in that group succeeding. It was noted that the patients who used a more violent method of suicide were in the low group of serotonin levels. This evoked the possibility that low serotonin levels could possibly be a predictor of suicide, however the interactions between these two concepts were unclear. The fact that this was in the cerebral spinal fluid implied that it is not only the brain that plays a part, but also the spinal cord. However, it could also be possible that the brain’s contribution plays a large enough part to be in the cerebral spinal fluid (Asberg, M., Träskman, L., & Thoren, P., 1976). It is also worth noting that serotonin is found to play a part in many other things, such as sleep, pain and aggressive behaviour, which incidentally are all involved in the symptoms of depression, especially the aggression, which links to methods and ways of suicide, and suicide itself as being an aggressive act. This may show that serotonin may not be directly