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Major Depressive Disorder Paper


The increasing rate of mental health issues around the globe has become a global concern. Recent statistics by NAMI show that in the year 2020, over 59.2 million people in the US will experience mental illness. The negations related to mental health, including being a risk factor for other diseases like cardiovascular diseases and inhibiting daily activities, have prompted many scientists and scholars to address the issue. Major Depressive Disorder (MDD) is one of the major mental illnesses affecting millions of people across the globe. According to the DSM-5 criteria, MDD can be defined as a mood disorder characterized by a persistent feeling of hopelessness, sadness, and lack of interest. According to NIMH, MDD affects around 8% of adults in the US every year. This paper is organized to discuss the causes and symptoms of MDD.


There are various symptoms of MDD as stipulated by both DSM-5 criteria and ICD-10 criteria. These symptoms are essential in the diagnosis and treatment of MDD. According to DSM-5 criteria, MDD is characterized by the following symptoms; depressed mood most of the day almost every day; lack of interest in activities they were interested in, including pleasure activities like sex or leisure activities like football practically all day every day; significant weight loss or weight gain (5% increase or decrease) not resulting from either dieting or exercising; insomnia or hypersomnia almost every day; Fatigue not emanating from excessive work and psychomotor agitation or retardation (Uher et al., 3) Further, feeling of worthlessness and decreased ability to think or concentrate are also listed as symptoms of MDD. Finally, suicidal ideation is also listed as a significant symptom of MDD. The DSM criteria argue that for diagnosis of MDD, five or more of the symptoms mentioned above must be present consistently for two weeks, with at least one symptom being a depressed mood or lack of interest (Uher et al., 3)

The ICD 10 criteria list the same symptoms but approach the diagnosis of the disease differently. The ICD 10 criteria argue that for the diagnosis of MDD, the patient must show at least two of the following symptoms; depressed mood, lack of interest, and fatigue (Gruenberg et al., 6). Further, the criteria outline that the patient must also have at least one of the other symptoms mentioned above (Gruenberg et al., 6)

DSM criteria also list the depression symptoms in children, adolescents, and adults. The MDD symptoms in children include; weight loss, irritability, agitation, sadness, unexplained aches in different parts of the body, and refusal to go to school (Bhatia & Bhatia). In older adults, the symptoms include; sadness, depressed mood, loss of interest, fatigue, suicidal ideation, and memory loss.

Causes and Risk Factors

Like many other mental illnesses, the exact cause of MDD is still unknown. However, scientists around the globe have concocted possible causes of this menace. First, there is a strong relationship between genetics and MDD. Research has shown that a person with a close relative with depression is more likely to contract the illness than a person without a relative with depression (Flint et al., 484). Further, a group of scientists identified a gene known as the depression gene that is believed to cause depression. The depression gene, chromosome 3p25-26, was found in more than 800 families with recurrent MDD. The research further identified that over 40% of people with depression could link it to genetics.

Further, growing up with someone with depression is also linked to contracting the disease later on. This aspect is more adamant between parents, caregivers, and children or siblings. This implies that growing up with a parent who has MDD increases the probability of contracting MDD.

Researchers also believe that brain chemistry plays a significant role in depression. Research by Harvard Medical School outlines that neurotransmitters have a significant viable relationship with depression (What causes depression?). The study outlined that various brain parts are essential in maintaining mood balance and, therefore, can lead to mood imbalance under multiple conditions. These parts include nerve cell connection, nerve cell growth, the functionality of nerve circuits, and brain chemistry (What causes depression?). The inter-functionality of these parts plays a role in depression and mood stability. The brain chemicals like neurotransmitters and their interaction with neuro-circuits also play a significant role in mood stability (Arango et al.).

Scientists and researchers also believe that hormones play a significant role in depression. Hormonal imbalance causes depression, especially in women. Research articulates that various hormones like estrogen and progesterone directly link to depression (Studd et al., 340). Progesterone, also known as relaxation hormone, produces a calming effect and, therefore, when in low supply, can result in depression, insomnia, hyper insomnia, anxiety, and fatigue. In men, various hormones like testosterone can also cause depression when in low supply (Studd et al., 340). Research associates depression in older adults with the low production of this hormone. Further, research articulates that men with low testosterone are four hundred times more likely to be diagnosed with depression than those with normal levels of this hormone (Amiaz et al.)

Further, researchers associate various biological differences with depression. Research shows that people with depression appear to have physical changes in the brain. The significance of the role played by these changes is yet to be discovered. However, scientists agree that they play a particular role in depression.

There are various risk factors for depression. These factors increase the probability of one contracting depression at a certain point in life. Different personality traits are associated with an increased likelihood of contracting the illness. These traits include; pessimism, low self-esteem, and overdependence (Dobson et al., 24). Further, experiencing a traumatic event such as witnessing a murder, the loss of a loved one, sexual abuse, and financial problems increases the risk of contracting the disease (Dobson et al., 37)

Other risk factors of contracting MDD include; chronic illnesses like cancer, HIV, stroke, or heart disease; a history of other mental health disorders like bipolar disorder, PTSD, and anxiety disorders; alcoholism and drug abuse; being bisexual, lesbian, or gay; and use of various medications like sleeping pills. Recent research has pointed out that depression is more prevalent in gay and lesbian relationships because of the form of social support these relationship minorities experience (Mustanski et al., 2426).


The issue of mental health affects a significant percentage of the world population. The economic and social impacts of the covid-19 pandemic have increased the probability of contracting mental health illnesses. As a result, mental health issues require increased attention by governments and scholars alike. MDD is one of the major mental health illnesses affecting many people around the globe. There are various symptoms of MDD, including depressed mood, lack of interest, and weight gain or loss. Although scientists have not established the causes of MDD, various studies articulate that genetics, brain chemistry, the functionality of the brain, hormones, and biological differences play a significant role in contracting the disease. There is a need for scientific research in this area to identify the causes and mitigation of MDD and therefore reduce its increasing prevalence. Additionally, there is a need for research regarding the diagnosis of MDD to avoid confusion since MDD has many similar symptoms to disorders like anxiety disorders. Scientists should develop scientific diagnostic measures that enhance the accuracy of the diagnosis.

Works Cited

“What causes depression? Onset of depression more complex than a brain chemical imbalance.” Harvard Health Publishing. (January 10, 2022). Retrieved from:

Amiaz, Revital, and Stuart N. Seidman. “Testosterone and depression in men.” Current Opinion in Endocrinology, Diabetes and Obesity 15.3 (2008): 278-283.

Arango, Victoria, Mark D. Underwood, and J. John Mann. “Serotonin brain circuits involved in major depression and suicide.” Progress in brain research 136 (2002): 443-453.

Bhatia, S. K., & Bhatia, S. C. (2007). Childhood and adolescent depression. American family physician, 75(1), 73-80.

Dobson, Keith S., and David JA Dozois, eds. Risk factors in depression. Elsevier, 2011.

Flint, Jonathan, and Kenneth S. Kendler. “The genetics of major depression.” Neuron 81.3 (2014): 484-503.

Gruenberg, Alan M., Reed D. Goldstein, and Harold Alan Pincus. “Classification of Depression: Research and Diagnostic Criteria: DSM‐IV and ICD‐10.” Biology of depression: From novel insights to therapeutic strategies (2005): 1-12.

Mustanski, Brian S., Robert Garofalo, and Erin M. Emerson. “Mental health disorders, psychological distress, and suicidality in a diverse sample of lesbian, gay, bisexual, and transgender youths.” American journal of public health 100.12 (2010): 2426-2432.

Studd, John, and N. Panay. “Hormones and depression in women.” Climacteric 7.4 (2004): 338-346.

Uher, Rudolf, et al. “Major depressive disorder in DSM‐5: Implications for clinical practice and research of changes from DSM‐IV.” Depression and anxiety 31.6 (2014): 459-471.


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