Major depression

Major depression is a psychiatric disorder characterized by a pronounced and persistent decline in mood that significantly impairs an individual’s daily functioning. Also known as clinical depression or major depressive disorder (MDD), this condition is not merely a temporary state of sadness but a serious mental health issue that disrupts functioning and requires intervention. According to the World Health Organization, major depression is one of the most common mental disorders worldwide and can lead to impairments in personal, social, and occupational domains. ^【1】

Definition and Diagnostic Criteria

Major depression is defined according to the criteria outlined in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), published by the American Psychiatric Association. For a diagnosis to be made, at least five of the following symptoms must be present for a minimum of two weeks, with at least one of them being either “depressed mood” or “loss of interest or pleasure”:

• Depressed mood for most of the day, nearly every day
• Markedly diminished interest or pleasure in all or almost all activities
• Significant weight loss or gain, or decrease or increase in appetite
• Insomnia or hypersomnia
• Psychomotor agitation or retardation
• Fatigue or loss of energy
• Feelings of worthlessness or excessive or inappropriate guilt
• Diminished ability to think or concentrate, or indecisiveness
• Recurrent thoughts of death, suicidal ideation, or a suicide attempt

These symptoms must not be attributable to substance use, another medical condition, or bereavement, and they must cause significant impairment in social, occupational, or other important areas of functioning.

Epidemiology

Major depression is a highly prevalent mental disorder worldwide. According to World Health Organization data from 2021, approximately 280 million people globally experience depression. The prevalence rate is nearly twice as high in women as in men. Although it typically begins in late adolescence or early adulthood, it can occur at any age. ^【2】

Etiology and Risk Factors

Multiple biological, psychological, and environmental factors contribute to the development of major depression:

Biological Factors

Genetic predisposition, imbalances in brain chemistry (particularly serotonin, dopamine, and norepinephrine levels), and hormonal changes may play a role in the onset of major depression. Structural and functional differences have also been observed in certain brain regions, such as the prefrontal cortex and hippocampus. ^【3】

Psychological Factors

Individual traits such as cognitive distortions, low self-esteem, and inadequate coping mechanisms in response to adverse life events can increase the risk of major depression. According to Beck’s cognitive theory, a negative cognitive triad—negative views of the self, the world, and the future—creates a foundation for depression.

Psychotherapy

Approaches such as cognitive behavioral therapy (CBT), interpersonal therapy (IPT), and psychodynamic therapy aim to restructure thought patterns and emotional processing. For mild to moderate depression, psychotherapy alone may be sufficient.

Other Interventions

In severe cases, biological interventions such as electroconvulsive therapy (ECT), transcranial magnetic stimulation (TMS), and ketamine treatment may be employed. Additionally, lifestyle modifications, social support, and regular physical exercise can serve as protective factors that support treatment.

Cultural and Social Dimensions

The expression of depression varies across cultures. In some societies, depression is primarily manifested through physical symptoms, while in others, psychological complaints are more prominent. Stigma, limited access to mental health services, and societal gender roles can also influence diagnosis and treatment processes.