Depression is, along with anxiety disorders, one of the most frequent and well-known disorders or psychopathologies worldwide throughout history. Research regarding what exactly it is and what causes it has is therefore something very relevant for the scientific community and the population in general. Based on the data reflected by the research, a large number of explanatory models have been proposed that take into account both biological and environmental factors.
Among the former, attempts to explain depression as a product of problems in the balance or levels of certain neurotransmitters are common. And among these hypotheses, one of the most popular and recognized is the serotonergic hypothesis of depression
Serotonin is one of the main and best-known neurotransmitters present in the brain. This hormone, which in addition to the nervous system can be found in other body systems (in fact most of the serotonin in our body is found outside the nervous system, especially in the digestive tract), was one of the first neurotransmitters to be identified It is synthesized from tryptophan, which in turn can be introduced into the body through the diet.
Among the numerous functions it performs, it is considered linked to the regulation of circadian rhythms and energy levels (especially due to its important presence in the suprachiasmatic, ventromedial and paraventricular nuclei), thermal control, appetite, libido. , relaxation and sensations of well-being and comfort. It is also considered one of the main hormones linked to maintaining mood, being altered in those people who have depressive-type problems.
The serotonergic hypothesis of depression is one of the best-known biological hypotheses that attempts explain the causes of depression It proposes that the causes of depression are a deficit or lack of serotonin in the brain. This theory is based on the role of serotonin in the regulation of mood, indicating that a decrease in serotonin levels in the nervous system or in key points such as the limbic system would be responsible for depressive symptoms.
Likewise, the so-called permissive serotonin hypothesis indicates that The alteration and decrease in serotonin at the brain level generates dysregulation of other neurotransmission systems, such as noradrenaline. It is part of the monoaminergic hypotheses, which state that the mental alterations typical of depression are due to poor functioning, synthesis or transmission of neurotransmitters such as serotonin and catecholamines (dopamine and norepinephrine).
Pharmacological treatments
When treating depression, different models and techniques have been used, both at the psychotherapy level and at the pharmacological level. In this last aspect, The main psychotropic drugs used for the pharmacological treatment of depression They are those that regulate or alter monoamine levels, with those that increase serotonin levels being especially used.
Specifically, today the most common psychotropic drugs when it comes to combating depression are SSRIs, Specific Serotonin Reuptake Inhibitors. This is a group of drugs whose main mechanism of action is (as its name suggests) to prevent presynaptic neurons from recapturing or absorbing the serotonin they have emitted, so that it remains in the synaptic space and the level of serotonin is generally increased. this neurotransmitter in the brain.
Despite this, it must be taken into account that serotonin is not the only neurotransmitter involved, and that there are alternatives that focus on stimulating the levels of other substances, whether secondary or primary. For example, drugs that, in addition to serotonin increase norepinephrine levels the SNRIs, generating an equivalent level of symptomatological improvement.
Nor should we forget that pharmacological treatment generates changes in the brain that reduce symptoms, but generally do not treat the underlying problem that the person themselves links to depression (for example, the absence of reinforcers, low perception of control, prolonged stress or anxiety). Psychological therapy has been shown to be more effective in the long term which suggests that depression is not a merely serotonergic problem.
Caution: we are talking about a hypothesis
The existence of alterations in serotonin levels in the brain is documented, and it is assumed that one of the main neurobiological problems presented by patients with depression is a serotonin deficiency. It has also been observed that The decrease in the levels of this hormone generates depressive symptoms
However, it is still true that these deficits are simply linked to depressive symptoms, without necessarily being the cause. In fact, the causes of depression are not yet fully known, being generated by the combination of biological and socio-environmental elements. Likewise, other neurotransmitters have been found related to depressive symptoms or that may participate in their improvement, such as norepinephrine, dopamine or GABA.
Thus, it should not be assumed that the serotonergic hypothesis describes the ultimate cause of depression, since there are many factors that play a role in its genesis. That is why today the serotonergic hypothesis has lost power and it has come to be seen not as the cause of depression but as the generator of a biological vulnerability to it.
The serotonergic hypothesis and the use of medications such as SSRIs have received numerous criticisms, among other aspects due to the fact that excessive attention has been focused on them and have greatly limited the development of other models and drugs. The debate about the real effectiveness of antidepressants in treating the problem itself is also widely known.
