According to World Health Organization (WHO) data, the global prevalence of depressive disorders is reported to be 3.8%, with a higher prevalence in adults at 5% (280 million people). Additionally, it has been noted that depressive disorders are more common in women than in men [1]. The reasons for this discrepancy are multifaceted, encompassing psychological, biological, and social factors. While one explanation suggests that the unequal position of women in many societies might contribute, it has been observed that rates of depression do not necessarily change significantly in societies where women have a more equitable status. Biologically, changes in hormone levels, particularly in women, are also considered potential contributors to the higher prevalence of depression in this demographic.

Depressive disorders include Major Depressive Disorder (MDD), Dysthymic Disorder (Persistent Depressive Disorder), and Premenstrual Dysphoric Disorder.

In psychiatry, standardized diagnostic approaches are essential for establishing a mutual understanding worldwide. The predominant diagnostic tools currently utilized include the 'Diagnostic and Statistical Manual of Mental Disorders (DSM-5)' and the 'International Statistical Classification of Diseases and Related Health Problems (ICD-11)' [2, 3].

For a diagnosis of MDD according to DSM-5 criteria, a patient must show symptoms for at least two weeks and have at least five of the nine specified symptoms, including at least one of the first two symptoms. The identified symptoms are: 1. Depressed mood, 2. Loss of interest or lack of pleasure in almost all activities, 3. Changes in appetite (either decrease or increase), 4. Insomnia or excessive sleeping, 5. Slowness or agitation in movements, 6. Low energy, 7. Feelings of guilt, 8. Difficulty concentrating or indecisiveness, 9. Thoughts or plans of death/suicide. The diagnosis is further nuanced by considering accompanying symptoms or conditions. For instance, if anxiety is presented, it might be termed depression with anxious distress. If symptoms include loss of pleasure, severe depression, worsening in the mornings, early morning awakening, weight loss, and guilt, it might be labeled as melancholic depression. Depression with seasonal pattern is noted when depressive episodes occur during specific seasons. This comprehensive evaluation allows for a more precise characterization of depressive disorders based on individual symptomatology.

Dysthymic disorder is characterized by milder symptoms than MDD but follows a chronic course. Many patients report feeling as if they have "always been like this," as the onset typically occurs in adolescence or the 20s. According to DSM-5 criteria, a diagnosis of dysthymic disorder requires symptoms to persist for at least two years. In addition to a depressed mood, the presence of at least two of the following symptoms is necessary: 1. Decrease or increase in appetite, 2. Insomnia or excessive sleeping, 3. Low energy, 4. Low self-confidence, 5. Attention deficit, 6. Feelings of hopelessness. This extended duration and the presence of chronic, albeit less severe, symptoms distinguish dysthymic disorder from major depressive episodes. The persistent nature of these symptoms over an extended period contributes to the chronicity of the disorder.

Premenstrual Dysphoric Disorder (PMDD) is characterized by symptoms similar to those seen in other depressive disorders. However, what distinguishes PMDD is that these symptoms specifically manifest in the last week before the onset of menstruation and notably improve within a few days after menstruation begins.

The mourning process is an essential consideration in the differential diagnosis of depression. Grief following a significant loss is not categorized as a mental illness, and individuals experiencing normal bereavement are not diagnosed with depressive disorder even if they meet the criteria for it. However, it is worth noting that some individuals may develop MDD during the mourning process. Individuals going through a normal mourning process might still exhibit reactions to their environment and experience positive emotions. Unlike those with depression, they typically do not show a psychomotor retardation, intense feelings of worthlessness or guilt are less frequent, and suicidal thoughts are less common. By carefully observing these distinctions, healthcare professionals can better differentiate between normal grief reactions and depressive disorders.

Untreated depressive episodes tend to last around 6-12 months, but with appropriate treatment, the duration is often reduced to approximately 3 months. The progression of the disease may lead to more frequent and prolonged depressive episodes over time. Positive factors influencing the course of depressive disorders include low disease severity, the absence of other comorbid psychiatric or medical conditions, good treatment adherence, and strong social support. On the flip side, negative factors associated with a more challenging course include the presence of comorbid psychiatric conditions (e.g., anxiety disorder, alcohol or substance use disorder), personality disorders, a history of multiple hospitalizations, and the onset of the disease at an older age [8]. 

Treatment options mainly include pharmacotherapy and psychotherapy. In addition, neurostimulation methods (vagal nerve stimulation, transcranial magnetic stimulation (TMS), deep brain stimulation (DBS), electroconvulsive therapy (ECT)), and phototherapy (bright light therapy) are among the methods that can be preferred.