Major Depressive Disorder: Physiological Root of the Problem and the Action of Medication

Major Depressive Disorder: Physiological Root of the Problem and the Action of Medication

Evidently, depression is a widely used term in the society. In fact, it is often associated with the accumulation of negative emotions, hence being commonly identified as a problem of psychological basis (Stahl, 2008). The major depressive disorder (MDD) is of course under the classification of depression based problems. Otherwise called as unipolar depression, MDD is characterized by symptoms such as constant depression, minimal interest and pleasure, drop in weight due to reluctance in terms of eating, sleeping disorders, expression of guilt, and suicide attempts (Stahl, 2008). With such symptoms, it is easy to assess the severity of the problem and in fact it may even be considered as life threatening.

In this sense, it is evident as to why scientific researches regarding MDD are being conducted. In addition, there are still many possible sources or roots of the problem such as genetic basis and immunological explanations that are still being assessed and considered, hence implying that up to now MDD is still not yet completely understood and mapped out (Stahl, 2008). It is evident however that drugs or medications such as serotonin re-uptake inhibitors (SSRIs) have been produced that have been viewed as generally effective in cases of MDD. Hence, it is apparent that although there are many potential causative agents and explanations regarding the occurrence of MDD, there are indeed more established ones. In this case, the concept of MDD as a manifestation of physiological changes in the brain, specifically in terms of the neurotransmitters and neurons have in effect led to the development of SSRIs as such drugs act upon based on this understanding of MDD. Therefore, in order to attain a general understanding regarding how MDD is currently being treated and controlled, it is vital to assess MDD in terms of the neurotransmitter and neurons hypothesis and the actions in which SSRI drugs control MDD.

The brain is of significant role in the manifestation in depression. In fact, changes in the brain especially in relation to shifts in the levels of substances in the brain lead to the occurrence of psychological problems. Taking into consideration that the brain is a vital component of the nervous system and is in fact the main organ that controls all the other components of the body, then it is not surprising that such changes in actions, mood, and even perception is exhibited when changes in the brain occur. In a more specific sense, when unfavorable changes in the components of the brain such as the neurotransmitters and the neurons occur, then expectedly psychological problems are one of the most common results (Stahl, 2008).

Neurons are of course the minute components of the brain in which signals travel through, these signals or information are distributed through the actions of the neurotransmitters which are generally considered as chemical substances dispersed throughout the brain and the nerves (Stahl, 2008). Hence, it is important that the normal functions and flow of information between neurons are maintained by the neurotransmitters. In addition, since the neurotransmitters are vital in the proper transmission of specific signals throughout the neurons, some functions of specific neurotransmitters have in fact already been determined. In fact, seven have been directly linked with functions for emotion and behavior which includes acetylcholine, dopamine, norepinephrine, epinephrine, serotonin, gamma-amino butyric acid, and endorphins (Stahl, 2008).

Although as discussed, several neurotransmitters have been linked with specific roles regarding emotions, is evident that serotonin is characteristically the neurotransmitter that controls the functions that best fits the symptoms experience by an individual having a case of MDD. In fact, serotonin is associated with functions of mood control, tendency to sleep, perception of food, and behavior (Stahl, 2008). Having established, the relation of the neurotransmitter serotonin to that of the symptoms characterized in MDD, it is now proper to discuss how the problems in MDD occur in relation to serotonin. It has long been established through studies that the levels of serotonin are rather varied, and the effects of different levels of serotonin has also been determined to be non uniform throughout humans; however, from the studies, there has been a generalization that the most individuals have experienced harmful emotional and behavioral based effects from lowered levels of serotonin (Stahl, 2008).

Thus, it is a fact that the occurrence of the MDD, along with the manifestation of its symptoms which mainly includes episodes of depression and thoughts of committing suicide as discussed, is greatly due to the lowered presence of serotonin in specific parts of the brain. In relation to this, a question regarding the reasons as to why serotonin levels are significantly diminished comes to mind. Neurotransmitters also require a mode of transport in order to be utilized and taken into the neuron. In this sense, given that neurotransmitters such as serotonin have no innate means of transport, specialized transporters are required for this task; to expound, specialized transporters take advantage of the sodium potassium pump in order to efficiently transfer serotonin into the neurons despite the process requiring energy in order to progress (Stahl, 2008).

In relation to the process of moving the serotonin, it is made apparent that the regulatory effects of serotonin do occur upon its free state outside the neuron, and not while being maintained inside it. The probable reason for the continuous depletion of serotonin levels is that there are dietary requirements in order to produce serotonin such as typtophan, as well as the fact that the process in which it is bound to the neuron continuously occurs regardless of the amount of serotonin (Stahl, 2008). Given that the requirement for the process of transportation to occur is the maintenance of the sodium potassium pump system, then it may be inferred that as long as the system functions, then further reduction in serotonin levels is exhibited which as discussed leads to the manifestation of the problems associated with MDD.

SSRIs, such as Prozac, Effexor XR, Serzone, Zoloft, and Lexapro, have all been developed in order to counteract the effects of the transporters of serotonin. As mentioned, the presence of the sodium potassium pump allow for the process of transport to continue. In relation to this, studies have assessed that the capability of the transporter to utilize the sodium potassium pump is controlled by its capacity to become activated by the presence of sodium (Stahl, 2008). In fact, if the presence of sodium is lost then the tendency of the transporter to bind with serotonin is lost as well. The SSRIs function in relation to this aspect. Given that the transporter has several binding sites and is dependent upon bound sodium in order to facilitate transport functions, then the active ingredient of the SSRI, binds into one of the available binding sites and in result inhibiting the capacity of the transporter to bind with sodium (Stahl, 2008).

From the points made in the discussion it is apparent that even though MDD is characterized by behavioral and psychological manifestations, its roots are indeed of physiological basis. In this sense, the importance of the biochemical functions and processes in the brain is further supported due to the fact that most processes that occur in the brain result in direct actions or consequences for an individual. In addition, the importance and degree of effects of the biochemical actions of the components in the nervous system is further exemplified in this case as the drugs aimed towards stopping the effects of MDD mainly functions for terminating the biochemical reaction and binding capabilities of the transporter. Therefore, from the discussion of MDD, its physiological based roots, and the actions of SSRIs, it is in a way implied that disorders of the psychological variant are of biological basis and can be scientifically explained through processes in physiology.


Stahl, S.M. (2008). Stahl’s Essential Psychopharmacology: Neuroscientific Basis and Practical Applications. New York, United States of America: Cambridge University Press.

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