Introduction
The affective disorder is an umbrella term that includes the list of various psychiatric issues negatively affecting a person’s mood. The set of affective disorders ranges from all kinds of depression and anxiety to bipolar disorder and post-traumatic stress disorder. In medicine, major depressive disorder (MDD) is the most frequent type of depression and refers to a state of persistent downheartedness and hopelessness, exhaustion, and poor mood.
In nature, mental diseases collectively known as affective disorders, including MDD, are multifactorial and have a number of genetic and environmental components. It means that biological and psychological components influence affective disorder appearance. For instance, some depressive disorders, such as postpartum depression or Seasonal Affective Disorder (SAD), indicate the predominant role of environmental factors in their occurrence. On the contrary, bipolar disorder, a mental illness that causes a person to suffer mood swings from mania to depression, is tightly connected to genetic factors.
This paper aims to review recent findings on the nurture versus nature on diagnosis and depression treatment and summarize hereditary factors that can lead to MDD. Disputes about character and education are based on people’s sociobiological nature, personality, cognitive qualities, temperament, and psychopathology. Since preprogrammed, genetics and other biological factors impact human physical and mental health and regulate their behavior. The term nurture refers to the impact of environmental factors, such as exposure, experience, and education, on a person after conception.
According to the nurture theory, there are links between environmental factors and psychological results. For example, children learn to read more effectively if they have plenty of time spent reading to them from a young age. On the other side, Behavioral genetics depicts the high impact of genetic factors as the cause of human behavior and claims biological influence is more potent than nurture. However, most medical workers treating affective disorders consider nature and nurture equally and apply medical and psychiatric methods.
MDD as Multifactorial and Polygenic Disorder
Polygenic genetic effects are the result of the interaction of many genes. Genes at multiple loci determine complex features not influenced by environmental factors in polygenic inheritance. The scientific community is investigating the cumulative effects of these genes since no single gene is considered dominant or recessive over another (Lopizzo et al., 2015). On the other hand, multifactorial inheritance is a trait influenced by more than one gene and environmental variables (Davis et al., 2021). These entities are generally viewed as single entities because there is rarely a clear separation.
Heredity plays a significant role in the risk of depression and the development of severe forms of the disease. By studying identical twins and their families, scientists have shown that depression is inherited with a 37 percent chance (Husain et al.,2020). The risk of inheriting depression is 2-3 times higher in descendants of the first degree of the relationship (Husain et al.,2020). In addition, severe forms of depression develop more often in people who have a genetic predisposition (Husain et al.,2020). Modern research has received enough material to ascertain the presence of genes that cause mood disorders.
For half a century, scientists have been trying to discover the genes responsible for the occurrence and development of MDD. A 2015 study examined “more than 100 potential genes for putative links between their alleles and the possibility of causing depression or its symptoms” (Lopizzo et al., 2015, p. 2). However, only a few candidate genes have been identified that could predict a genetic predisposition to MDD (Lopizzo et al., 2015). Thus, although a hereditary factor is prominent, due to the complex process of intertwining genes, it is difficult to identify specific candidate genes.
The influence of environmental factors on depression has been studied in more detail and shows a significant relationship between the psychological state and the triggering of depression mechanisms. For example, early life stressful experiences (ELS) are one of the pronounced factors in the development of MDD. Scientists believe that ELS manifests itself in depression and other mental disorders, not in all people, due to a combination of genetic predisposition with psychological trauma (Lopizzo et al., 2015). Hence, heredity determines the risk of developing affective disorders, but external factors often trigger them.
The loss of a loved one, medical illness and injury, disability and functional decline, and a lack of social engagement have been crucial psychosocial risk factors for late-life depression disorders. According to Mullins and Lewis, these psychological depression risk factors might be exacerbated or protected depending on the individual and the situation in which they are experienced (Mullins & Lewis, 2017). Studies of the psychological state of medical workers during the coronavirus pandemic revealed the relationship between depression and prolonged stress of social isolation (Zhou et al., 2020). The long-term effects of stress associated with concerns about one’s health and financial well-being are also positively correlated with the development of depression (Zhou et al., 2020). Any prolonged unpleasant psychological conditions negatively affect mood and its regulation.
Physiological factors may be the cause of depression and other affective disorders. Overworking, insomnia, lack of daily routine, and an unhealthy diet correlate with increased risks of MDD (). Moreover, a weak immune system, hormonal disorders, heart disease, weight gain, and physical discomfort are also factors in the development of depression (Sanches et al., 2019). In addition, physiological factors can not only trigger MDD, but depression itself aggravates a person’s physical health (Kennis et al., 2020). People with depression are caught in a vicious cycle of failing to take care of their health, the deterioration of which caused the mood disorder in the first place (Golberstein et al., 2019). In such cases, therapy includes the normalization of physical condition, hormones, sleep and rest, and other lifestyle factors.
Depression can be treated with medication or therapy to eliminate all symptoms. Many people are unaware of the various treatment choices for depression and the consequences of not getting help for it. For those depressed, learning more about the illness and the long-term effects of not getting treatment is a valuable resource (Sanada et al., 2020). Depression that goes untreated can make it challenging to form new connections or sustain old ones. Those with long-term depression that has not been addressed may begin to isolate themselves from the rest of the population. Depression may make even the most fundamental tasks in life, such as having a conversation with a stranger, seem impossible (Dalgleish et al., 2020). Depression that is not handled can lead to a patient’s isolation and apathy. It is common for business and personal relationships to suffer when this occurs.
Currently, both screening and treatment of depression occur both medically and psychologically. When diagnosing depression, the patient is offered various psychological and blood tests, checking the main physiological risk factors (Han et al., 2018). First of all, the state of the hormonal system and the presence of various endocrine disorders are checked. In the treatment of depression, drug therapy is also used, which helps to level the symptoms, and psychotherapy (Van Rheenen et al., 2020). A combination of approaches has shown the best efficacy in the treatment of MDD since both physiological and psychological factors cause depression. Environmental, behavioral, and psychological principles are used in conjunction with clinical therapies in Lifestyle Medicine to improve physical and mental health. This could also be a way to promote health and possibly prevent depression.
Emotional and cognitive processes can be simulated using computational modeling. An increase in MDD hyperactivity was not reduced by contemporaneous activation. This hyperactivity is affected by predictable feedback to cognitive signals, emulating the mental impairment seen in MDD (Schickedanz et al., 2018). The computational model depicts how glutamate dysregulation can generate abnormal mental changes, respond to treatment, and be reproduced in EEG rhythms as MDD biomarkers (Sanches et al., 2019). Prenatal exposure to environmental stressors increases a child’s risk of developing psychopathology later in life, suggesting that genes and environment interact early in development. An individual’s risk for psychopathology may be influenced by hereditary and environmental aspects of a precise condition and the existence or unavailability of other protective variables, which may also alter the danger for future psychiatry (Zhou et al., 2020). Therefore, stressful early childhood exposures can considerably obstruct the establishment of adaptive mechanisms necessary to handle problems in adulthood and may also lead to unhealthy lifestyles, unfavorable interactive relationships, and poor health results.
Research on depression risk factors can now be done using DNA microchip technology, regardless of the theories on depression etiology that are currently accessible. This allows researchers to conduct genome-wide association studies (GWASs). Many patients with various developmental disabilities have been studied in GWAS. However, no specific loci are associated with MDD propensity. There is still no clear understanding of the primary pathways that lead to MDDs. As a result of this inability to precisely pinpoint the genetic links and causes, it is evident that depression is a complex, multifactor, heterogeneous mental illness (Zhang et al., 2022). A person’s propensity for developing Down syndrome has a high chance been influenced by a complex interplay between various genes and their interactions with their environment. Each gene may contribute only a modest impact to the disease’s pathophysiology.
Conclusion
Half a century of research on the nature of affective disorders shows a close interweaving of genetic, physiological, and psychological factors. Therefore, MDD and other mood disorders are studied, diagnosed, and treated at the intersection of genetics and psychiatry. Developmental psychologists need to look at the interplay between nature and nurture in the context of a new age in the study of human biology and fundamental concerns about parenting to understand human growth and development. Genetic potential begins at conception and grows with the surrounding environment. As a person ages, the interplay between genes and the environment evolves.
In the case of treating MDD, it is impossible to separate nature from nurture in the human body and mind. Scientists have identified genes responsible for depression, but their activation is often due to environmental influences. On the other hand, the effect of physiological and psychological problems can change the brain’s biochemistry and cause MDD. When a cell is exposed to a particular environment, it determines which of the tens of thousands of genes it has access. To some extent, genes themselves and the byproducts of earlier protein synthesis influence the expression of other genes inside the cell.
Gene expression cannot be considered in isolation from the various contexts. There can be no other way to conceive the manifestation of genetic potential but in terms of the hierarchical structures that influence it. An organism’s genotypical individuality cannot be overlooked when thinking about its interactions with the environment. Nature cannot be considered in isolation from its environment. GWAS can preliminary look at the genetic architecture of traits or potential sites for further testing. Genetic polymorphism and the phenotypic distinction perceived between individuals in a species are of fundamental biological interest.
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