Depression – A Psychologist's Guide

Depression is one of the most common and debilitating mental disorders of our time. According to projections by the World Health Organization, by 2030, depression will become the leading cause of the global disease burden [1]. It is not mere gloom or temporary sadness—it is a serious medical disorder that requires professional treatment and can dramatically affect all aspects of a person’s life.

As a psychologist with experience treating mood disorders, I have prepared a guide to help you understand the nature of depression, recognize its symptoms, and learn about available treatment options. This article is based on scientific research and clinical guidelines, presenting the information in a way that is accessible to both patients and their loved ones.

What Is Depression? Definition and Scientific Basis

Depression is a mood disorder characterized by persistent sadness, a loss of interest in activities that were previously enjoyable, and a range of physical and cognitive symptoms that significantly impair daily functioning [2,3].

It is crucial to understand that depression is not a sign of weakness of character, nor is it something you can simply “pull yourself together” and overcome. It is a real medical disorder with a neurobiological basis that requires appropriate treatment, just like diabetes or high blood pressure.

The Neurobiological Basis of Depression

Contemporary research shows that depression is associated with complex changes in brain function. The traditional monoamine theory pointed to deficiencies in neurotransmitters such as serotonin, norepinephrine, and dopamine. However, the latest research suggests that depression is linked to more complex neuroregulatory systems and neural circuits that, in turn, influence neurotransmitter systems.

Imaging studies of the brains of people with depression reveal characteristic structural and functional changes, including increased hyperintensity in subcortical regions and reduced metabolism in the left anterior portion of the brain. These findings confirm that depression has a measurable, physical basis in the brain.

Classification According to International Standards

Depression According to the DSM-5

According to the DSM-5 (Diagnostic and Statistical Manual of Mental Disorders), depression falls under the category of mood disorders.

To diagnose Major Depressive Disorder, the clinician must identify the presence of at least five of nine symptoms that persist for a minimum of two weeks. Importantly, these changes must be noticeable compared to the person’s previous functioning, and one of the symptoms must be depressed mood or a loss of interest in activities that were previously enjoyable. Additionally, it is important to verify other criteria as well.

Core Criteria for Depression According to the DSM-5 (5 out of 9)

• A low mood that lasts for most of the day, almost every day.
• Loss of interest in daily activities—things that used to bring joy no longer do.
• Changes in appetite or weight that are not due to diet or illness.
• Sleep difficulties—these can manifest as insomnia or excessive sleepiness.
• Feelings of guilt, hopelessness, or low self-worth, often out of proportion to the situation.
• A slowing down or, conversely, increased motor activity that is noticeable to those around the person.
• Problems with concentration, decision-making, and memory.
• A feeling of fatigue and lack of energy almost every day.
• Thoughts of death or suicide—if you experience them, seek help immediately.

Additional criteria required for diagnosis:

• The symptoms must significantly impact daily life—at work, school, in relationships, or in other important areas.
• There have been no episodes of mania or hypomania in the past (unless they were caused by, for example, substance use).
• The symptoms are not caused by another illness or the effects of psychoactive substances.
• The person's condition is not due to other psychotic disorders, such as schizophrenia or schizoaffective disorder.

Depression According to ICD-10

The International Classification of Diseases (ICD-10), which is used in Poland, also includes detailed diagnostic criteria for depressive episodes, classifying them according to severity as mild, moderate, and severe.

The Epidemiology of Depression – The Scale of the Problem

Depression is one of the most common mental disorders in the world. Epidemiological data reveal the dramatic scale of this problem and its growing significance for public health.

Global Distribution

According to research, the percentage of people in the population who have ever met the diagnostic criteria for depression ( lifetime prevalence) ranges from 5 to 17 percent, with an average of about 12 percent [2]. This means that, statistically, one in eight people will experience a depressive episode requiring treatment at some point in their lives.

Particularly concerning are the figures showing an increase in the incidence of depression among young people. Although the average age of onset for depression is around 40, recent studies show an upward trend in incidence among younger age groups, which may be linked to the use of alcohol and other psychoactive substances [2].

Gender Differences

One of the most consistent findings in the epidemiology of depression is that its prevalence is twice as high among women as among men [2]. This difference is observed across all cultures and age groups, suggesting both biological and psychosocial mechanisms.

The causes of this disparity are multifaceted and include:

• Hormonal changes, particularly those related to the menstrual cycle, pregnancy, and menopause
• Differences in Patterns of Psychosocial Stress Between Women and Men
• Differences in Ways of Coping with Stress
• The Influence of Social Roles and Cultural Expectations
• Differences in Reporting Symptoms and Seeking Help

Demographic and Social Factors

Epidemiological studies also reveal other important patterns in the prevalence of depression:

Marital status: Depression is more common among people who lack close interpersonal relationships, as well as among those who are divorced, separated, or widowed. Strong social ties act as a protective factor against the development of depression.

Geographic Location: It is interesting to note that depression is more common in rural areas than in urban areas, which may be related to limited access to health care, greater social isolation, and the specific stresses associated with rural life.

Socioeconomic status: Contrary to some stereotypes, studies do not show significant differences in the prevalence of depression among different racial groups or socioeconomic classes, although access to treatment can vary considerably.

Comorbidity of Depression with Other Disorders

Depression rarely occurs in isolation. People diagnosed with depression often have comorbid disorders, which significantly complicate the clinical picture and treatment:

• Anxiety Disorders: They occur in 40–50% of people with depression
• Substance use disorders: Particularly common, creating a vicious cycle in which symptoms reinforce one another
• Obsessive-Compulsive Disorder
• Personality Disorders
• PTSD (post-traumatic stress disorder)

The presence of comorbid disorders significantly increases the risk of suicidal thoughts and behaviors, making comprehensive assessment and treatment even more critical.

Symptoms of Depression – How to Recognize the Disorder

I’ve mentioned the DSM-5 diagnostic criteria before, and I’ve devoted a fairly concise separate post to the criteria in the ICD-10 classification. It’s worth emphasizing, however, that there are no simple or universal formulas for diagnosing depression. Diagnosing this disorder can be a real challenge.

Depression often develops gradually, and its early symptoms can be subtle and easily mistaken for typical reactions to chronic stress, exhaustion, or life challenges. However, it is crucial to be able to distinguish between a temporary low mood and clinical depression, which requires specialized support.

Below is a more detailed description of the diagnostic approach based on ICD-10 to better illustrate what the process of diagnosing depression entails and why it can sometimes be so complex. At the same time, I strongly advise against self-diagnosis—if you suspect you have symptoms of depression, the best course of action is to talk to a specialist who can help you view the situation objectively and professionally.

Primary (axial) symptoms

According to the diagnostic criteria, there are three main symptoms of depression, at least two of which must be present for a diagnosis to be considered:

1. Low mood

This is not ordinary sadness, but a deep, persistent state of low mood that lasts for most of the day, almost every day. Patients describe it as a feeling of emptiness, hopelessness, gloom, or despair. It can also manifest as irritability.

2. Anhedonia

This is a significant loss of interest in or enjoyment of activities that were previously a source of joy. This applies not only to hobbies and entertainment, but also to basic daily activities, interpersonal relationships, and even eating and sex.

3. Reduced energy and increased fatigue

Patients experience intense fatigue that does not improve with rest. Even simple daily activities require a tremendous amount of effort. This fatigue is both physical and mental.

Additional symptoms

In addition to the core symptoms, depression manifests itself through a range of other symptoms that significantly impact daily functioning:

Cognitive symptoms:

• Impaired concentration and attention—difficulty focusing on tasks, reading, and making decisions
• Memory problems, especially working memory
• A slowing of thought or, conversely, a disturbing acceleration of the flow of thoughts
• Difficulty making even simple decisions

Changes in Emotions Experienced During Depression:

• Low self-esteem and a lack of self-confidence
• Feelings of guilt and low self-worth, often unwarranted or excessive
• A pessimistic, bleak view of the future
• Feelings of hopelessness and helplessness
• Irritability and increased sensitivity to criticism

Behavioral symptoms—changes in behavior associated with depression:

• Social withdrawal and isolation
• Neglecting professional, school, or household responsibilities
• Avoiding social activities
• Psychomotor retardation or, conversely, agitation and motor restlessness

Somatic symptoms

Depression also has a distinct physical component, which is often the first warning sign:

Sleep Disorders

• Insomnia, especially waking up early in the morning
• Excessive sleepiness (hypersomnia)
• Non-restorative sleep, frequent awakenings during the night
• Nightmares

Appetite disorders and changes in body weight:

• Significant loss of appetite and body weight (>5% per month)
• Or, conversely, an increased appetite and weight gain
• Taste and Smell Disorders

Neurovegetative symptoms:

• Constipation or diarrhea
• Headaches, often of the tension type
• Musculoskeletal pain without a clear somatic cause
• Dizziness
• A feeling of shortness of breath or a “lump in the throat”

Sexual Disorders:

• Loss of libido
• Erectile dysfunction in men
• Anorgasmia
• Avoiding physical closeness

Daily mood swings

A characteristic symptom of depression, particularly its endogenous forms, is circadian mood fluctuation. Patients typically feel their worst in the morning and at midday, with some improvement in the evening. This pattern is so characteristic that it constitutes one of the diagnostic criteria for melancholic depression.

Suicidal Thoughts and Behaviors

One of the most serious symptoms of depression is suicidal thoughts, which occur in 40–80% of patients with depression. They can take various forms:

• Passive thoughts about death (“It would be better if I weren’t alive”)
• Active suicidal thoughts without a specific plan
• Suicidal thoughts accompanied by a plan
• Suicide attempts

It is important to understand that suicidal thoughts are not a sign of weakness or selfishness, but a symptom of an illness. Approximately 20–60% of people with depression attempt suicide, which makes assessing suicide risk a key component of any diagnosis of depression.

Symptoms in Different Age Groups

Children and Youth

• Irritability Instead of Sadness
• Problems at school and a drop in grades
• Withdrawal from peer activities
• Somatization (frequent stomachaches, headaches)
• Rebellious Behavior

Older adults

• Greater emphasis on somatic symptoms
• Memory problems that may indicate dementia
• Higher risk of suicide
• Frequent comorbidity with somatic diseases
• Social isolation

Causes of Depression – A Multifactorial Model

Depression is a disorder with a complex etiology that cannot be fully explained by any single biological or environmental factor. The current understanding of depression is based on a multifactorial model that takes into account the interactions between genetic predispositions, environmental factors, psychological factors, and biological factors.

Biological Factors

Genetics and Heredity

Family, adoption, and twin studies unequivocally confirm the role of genetic factors in the development of depression. The risk of developing depression among individuals whose parents or siblings suffer from this disorder is 2 to 3 times higher than in the general population [2].

Studies of identical twins are particularly compelling, as they show very high concordance rates for depression. Even when identical twins are raised separately, the risk of one of them developing depression increases significantly if the other suffers from the disorder.

Contemporary genetic research is attempting to identify specific genes responsible for susceptibility to depression. Although no single “depression gene” has been found, genome-wide association studies(GWAS) have identified hundreds of genetic variants that, taken together, may account for part of the heritability of depression.

Neurotransmitters and Neural Systems

The classic monoamine theory of depression focused on deficiencies in serotonin, norepinephrine, and dopamine. Although simplified, this theory remains clinically relevant, as evidenced by the effectiveness of antidepressants that act on these systems.

However, the latest research points to more complex mechanisms:

GABA (gamma-aminobutyric acid): This major inhibitory neurotransmitter is reduced in people with depression in plasma, cerebrospinal fluid, and brain tissue. GABA likely exerts an antidepressant effect by inhibiting ascending monoamine pathways [2].

Glutamate and glycine: These major excitatory neurotransmitters also play a role in the etiology of depression. Drugs that antagonize NMDA receptors for glutamate exhibit antidepressant properties, which has led to the development of new therapies such as ketamine.

Neuromodulation systems: Current theories focus on disruptions in the complex neural circuits responsible for regulating mood, motivation, and emotional processing.

Hormonal Disorders

The hypothalamic-pituitary-adrenal (HPA) axis plays a key role in the stress response and is often impaired in people with depression. Chronic activation of this axis leads to increased cortisol secretion, which can damage the brain structures responsible for regulating mood.

Other important hormonal disorders associated with depression include:

• Thyroid Disorders (Hypothyroidism and Hyperthyroidism)
• Growth Hormone Deficiency
• Sex Hormone Disorders (estrogens, testosterone)
• Disruptions in the circadian rhythm of melatonin

Structural and Functional Changes in the Brain

Neuroimaging studies have revealed characteristic changes in the brains of people with depression:

• Structural changes: A reduction in the volume of the hippocampus, the anterior cingulate cortex, and the prefrontal cortex. These areas are critical for regulating mood, memory, and executive function.
• Functional changes: Reduced activity in the prefrontal cortex, particularly on the left side, and increased activity in the amygdala, which is responsible for processing fear and anxiety.
• Neuroplasticity: Depression is associated with reduced neuroplasticity—the brain’s ability to form new neural connections. This may explain the difficulty in learning new patterns of thinking and behavior.

Psychological Factors

The Theory of Learned Helplessness

The theory of learned helplessness, developed by Martin Seligman, suggests that depression develops as a result of experiencing uncontrollable, negative events. When a person repeatedly experiences situations in which their actions have no impact on the outcome, they may develop a sense of helplessness that generalizes to other areas of life [2].

Beck's Cognitive Theory

Aaron Beck proposed that depression stems from negative cognitive distortions—systematic errors in thinking that lead to a pessimistic interpretation of reality. Beck identified the “cognitive triad of depression”:

• A Negative Self-Image
• A Negative Interpretation of Experiences
• Negative expectations about the future

Interpersonal Theory

This theory emphasizes the role of problems in interpersonal relationships in the development and maintenance of depression. The main areas of concern include:

• Mourning and Loss
• Interpersonal Conflicts
• Deficits in social skills
• Life Transitions and Changes in Social Roles

Personality Traits

Certain personality traits increase the risk of developing depression:

• Neuroticism – a tendency to experience negative emotions
• Perfectionism—especially socially imposed perfectionism
• Low self-esteem and a lack of self-worth
• Pessimistic attribution style—the tendency to attribute negative events to internal, stable, and global factors

Environmental Factors

Stress and Life Events

Stress is one of the strongest risk factors for the development of depression. The following are particularly important:

Long-term exposure to stress, such as financial problems, relationship conflicts, or chronic illnesses, can lead to the exhaustion of the body's adaptive systems.

Traumatic life events, such as the death of a loved one, divorce, job loss, or a serious illness, can trigger a depressive episode in people who are predisposed to it.

Adverse childhood experiences (ACEs) have a particularly strong impact on the risk of developing depression in adulthood. They include:

• Physical, emotional, or sexual abuse
• Negligence
• Family Dysfunctions
• The Loss of a Parent
• Poverty

Socioeconomic Factors

• Poverty and Social Inequality
• Unemployment and Job Insecurity
• Social isolation and lack of support
• Discrimination and Stigmatization
• Housing Issues

Cultural Factors

• Cultural norms regarding the expression of emotions
• Social Expectations and Gender Roles
• Access to Health Care
• The Stigmatization of Mental Illness
• Social Support Systems

The Vulnerability-Stress Model

The current understanding of the etiology of depression is best described by the vulnerability-stress model. According to this model, depression develops as a result of the interaction between:

• Susceptibility (diathesis)—genetic, biological, and psychological predisposing factors
• Stress – environmental triggers

People with high vulnerability may develop depression even in the face of relatively minor stress, while those with low vulnerability may need significantly more stress to develop the disorder. This model explains why not all people exposed to similar stresses develop depression.

Protective Factors

It is also important to understand the factors that protect against the development of depression:

Biological factors:

• Good physical condition
• A Healthy Diet
• Regular Sleep
• Avoiding Psychoactive Substances

Psychological factors:

• High self-esteem
• Good stress management skills
• An Optimistic Mindset
• A sense of control over one's life
• Spirituality and the Meaning of Life

Social factors:

• Strong public support
• Stable interpersonal relationships
• Community Involvement
• Access to Health Care
• Economic stability

Understanding these protective factors is crucial for developing preventive and therapeutic strategies.

Types and Subtypes of Depression

Depression is not a homogeneous disorder—there are many different forms and subtypes that vary in terms of symptoms, course, and response to treatment. Understanding these differences is crucial for an accurate diagnosis and the selection of appropriate treatment.

Classification According to the DSM-5

Major Depressive Disorder (
) This is the most commonly diagnosed form of depression, characterized by the presence of at least one major depressive episode. The episode must last at least two weeks and significantly impair functioning in important areas of life.

Persistent depressive disorder
Formerly known as dysthymia, this is a form of depression with milder symptoms but a significantly longer duration—at least two years in adults and one year in children and adolescents. People with this disorder often describe feeling as though they “have always been sad” or “can’t remember the last time they felt good.”

Disruptive Mood Dysregulation Disorder (DMDD)
A disorder introduced in the DSM-5 that primarily affects children and adolescents. It is characterized by recurrent outbursts of anger that are disproportionate to the situation and a chronically irritable mood.

Premenstrual Dysphoric Disorder
A severe form of premenstrual syndrome in which depressive and anxiety symptoms appear during the luteal phase of the menstrual cycle and subside after menstruation.

DSM-5 Criteria

The DSM-5 also introduces a number of specifiers that allow for a more precise description of the nature of a depressive episode:

With melancholic traits

This subtype is characterized by particularly severe symptoms, including:

• Complete loss of pleasure (anhedonia)
• Lack of emotional response to positive events
• A noticeable decline in mood in the morning
• Waking up early in the morning (at least 2 hours earlier)
• Significant slowing or psychomotor agitation
• Significant loss of appetite or body weight
• Excessive or unwarranted feelings of guilt

With atypical features

Paradoxically labeled “atypical,” this subtype is actually quite common and is characterized by:

• Mood reactivity—improvement in response to positive events
• Significant weight gain or increased appetite
• Hypersomnia (excessive sleepiness)
• The sensation of “lead-weighted limbs”
• A Long-Term Pattern of Sensitivity to Interpersonal Rejection

With psychotic features

In severe cases of depression, psychotic symptoms may occur:

• Delusions (often related to depression—guilt, punishment, illness)
• Hallucinations (usually auditory, with negative content)
• Disorganized Thinking

With catatonic features

A rare subtype characterized by psychomotor disturbances:

• Stupor (absence of movement and speech)
• Catalepsy (muscle rigidity)
• Mutism
• Negativism
• Repeating movements or words

Postpartum Depression

The diagnostic criterion “onset in the perinatal period” refers to depressive episodes that begin during pregnancy or within 4 weeks after childbirth. Postpartum depression affects 10–15% of women and can have serious consequences for both the mother and the child.

Seasonal Affective Disorder (SAD)

The “seasonal pattern” diagnostic criterion describes depressive episodes that occur regularly at specific times of the year, most commonly in the fall and winter. This is likely related to circadian rhythm disturbances and a lack of light.

Classification According to ICD-10

In the diagnosis of depressive disorders, in addition to the DSM-5 classification, the international ICD-10 system (International Classification of Diseases, 10th Revision), developed by the World Health Organization (WHO), is also widely used. This classification is the officially recognized diagnostic system in Poland and is used in healthcare, medical records, and statistics. Below are selected ICD-10 codes related to depression, taking into account various forms and levels of symptom severity.

F32 – Depressive Episode

• F32.0 – Mild depressive episode
• F32.1 – Episode of moderate depression
• F32.2 – Episode of major depression without psychotic symptoms
• F32.3 – Episode of major depression with psychotic symptoms
• F32.8 – Other depressive episodes
• F32.9 – Depressive episode, unspecified

F33 – Recurrent depressive disorder

• F33.0 – Currently a mild episode
• F33.1 – Currently a moderate episode
• F33.2 – Currently experiencing a severe episode, without psychotic symptoms
• F33.3 – Currently experiencing a severe episode with psychotic symptoms
• F33.4 – Currently in remission
• F33.8 – Other recurrent depressive disorders
• F33.9 – Recurrent depressive disorder, unspecified

F34 – Persistent mood (affective) disorders

• F34.0 – Cyclothymia
• F34.1 – Dysthymia
• F34.8 – Other established mood disorders
• F34.9 – Persistent mood disorder, unspecified

F41.2 – Mixed anxiety and depressive disorders

Other Important Distinctions

Unipolar and Bipolar Depression

It is crucial to distinguish between unipolar depression (occurring on its own) and depression that occurs as part of bipolar disorder. In bipolar disorder, depressive episodes alternate with episodes of mania or hypomania.

Endogenous and Exogenous Depression

• Endogenous depression: of biological origin, often without a clear triggering factor
• Exogenous depression: reactive, triggered by external stressful events

Primary and Secondary Depression

• Primary: occurring as the main disorder
• Secondary: developing as a result of other diseases (somatic or mental)

Diagnosis of Depression

Interview

In the diagnosis of depressive disorders (as well as many others), the patient interview plays a crucial role. It is during this conversation that the specialist gathers the information necessary to make an accurate diagnosis and plan appropriate treatment. Gathering a detailed medical history allows for an assessment of the severity and duration of depressive symptoms, their impact on the patient’s daily functioning, and an understanding of the dynamics of mood changes over time. It is equally important to learn about past depressive episodes, previous forms of treatment, and the patient’s response to those interventions. Attention is also paid to possible triggering factors, such as stressful life events, and to family history, which may indicate a genetic predisposition. The interview should also cover somatic aspects—many depressive symptoms may stem from physical illnesses or result from the effects of certain medications or psychoactive substances. Taking all these elements into account allows for a better understanding of the patient’s situation and helps distinguish depression from other conditions that may resemble it but require different management.

Diagnostic Tools

Standardized questionnaires and diagnostic scales are a valuable supplement to clinical assessment in the diagnosis of depressive disorders. Although they do not replace a clinical interview or a specialist diagnosis, they allow for an objective assessment of symptom severity, track changes in symptoms over time, and support treatment decisions. Below, I discuss selected tools used in psychological and psychiatric practice.

Beck Depression Inventory – Second Edition (BDI-II) (Beck Depression Inventory)

One of the most commonly used self-assessment questionnaires for depression is a 21-item test that evaluates various aspects of the disorder, such as mood, feelings of guilt, sleep problems, and suicidal thoughts. Due to its simplicity and wide availability, this test is often found online and can be completed independently, which increases its popularity among people seeking a preliminary assessment of their mental state. It is worth noting, however, that in many cases, the first, original version of the test is made available, which may differ from later, updated versions in terms of content and clinical validity. Therefore, results should be interpreted with caution and—if in doubt—a specialist should be consulted.

The Beck Questionnaires for Children and Adolescents – 2nd Edition (BYI-2)

Developed by Aaron T. Beck, the BYI-2 battery consists of five questionnaires designed to assess various aspects of the emotional and social functioning of children and adolescents. These tools measure symptoms of depression, anxiety, anger, low self-esteem, and difficulties in interpersonal relationships. The questionnaires can be used independently or together as a single integrated form, allowing for flexible adaptation of the assessment to diagnostic needs. The BYI-2 is helpful in the early detection of emotional problems and in planning psychological support.

The test is available at: https://www.practest.com.pl/sklep/test/BYI-2

Depression Measurement Questionnaire (DMQ)

This tool, developed by Emilia Łojek, Joanna Stańczak, and Agnieszka Wójcik (2015), is intended for psychologists and can be used with both adults and adolescents aged 16–19. It consists of 75 statements reflecting key symptoms of depression, such as low mood, loss of energy, anhedonia, guilt, pessimism, and suicidal thoughts. The tool is effective for both clinical diagnosis and scientific research—it can be used for screening, individual diagnosis, and monitoring treatment progress. The assessment can be administered individually or in groups, with no time limit.

The test is available at https://www.practest.com.pl/sklep/test/KPD

Set of Questionnaires for the Diagnosis of Depression in Children and Adolescents (CDI-2)

Developed by Maria Kovacs and adapted in Poland by Emilia Wrocławska-Warchala and Radosław Wujcik (2017), CDI-2 includes three versions of the questionnaire (self-report, parent, and teacher) used to assess symptoms of depression in children and adolescents aged 7–18. The tool can be used individually or in groups; after training by a psychologist, teachers can administer the assessment on their own. The CDI-2 provides measures of the severity of emotional problems and functional difficulties, supporting both clinical diagnosis and the monitoring of treatment outcomes. The kit is particularly useful for psychologists, psychiatrists, and pediatricians, as well as educators and nursing staff.

The test is available at https://www.practest.com.pl/sklep/test/CDI2 

Emotional Control Scale (CECS)

The scale, developed by Maggie Watson and Steven Greer and adapted into Polish by Zygfryd Juczyński, is used to assess the subjective ability to control emotions—anger, anxiety, and depression—in stressful situations. It can be used with both healthy individuals and those struggling with somatic illnesses. The tool is intended for adults and can be used individually or in groups; it takes an average of about 10 minutes to complete. The scale is included in the NPPPZ (Measurement Tools in Health Promotion Psychology) set and is particularly useful for psychologists, psychotherapists, educators, sociologists, and medical personnel working in mental health and providing support in difficult situations.

Test available at: https://www.practest.com.pl/sklep/test/CECS

The Hamilton Depression Rating Scale (HAM-D).

A scale completed by a specialist, particularly useful in clinical trials and for monitoring treatment response.

A 1960 article illustrating the scale of https://pmc.ncbi.nlm.nih.gov/articles/PMC495331/

Patient Health Questionnaire (PHQ-9).

A brief, 9-item assessment tool based directly on the DSM-5 criteria, often used in primary care.

Differential Diagnosis

Laboratory Tests

Although there are no specific laboratory tests that can definitively diagnose depression, blood tests and other medical tests can help rule out somatic causes of depressive symptoms, such as hormonal disorders, thyroid diseases, vitamin deficiencies, or neurological disorders. This makes it possible to identify the source of the symptoms more accurately and select an appropriate treatment plan.

• Complete Blood Count: Rule out anemia, which can cause fatigue and symptoms similar to those of depression.
• TSH and thyroid hormones: Both hypothyroidism and hyperthyroidism can cause symptoms of depression.
• Vitamin B12 and folic acid: Deficiencies in these vitamins can lead to depressive and cognitive symptoms.
• Blood glucose levels: Diabetes may be associated with an increased risk of depression.
• Cortisol: People with disruptions in the circadian rhythm of cortisol secretion may be at greater risk for depression, and restoring normal levels of this hormone may be beneficial for people with depression.

Conditions That Should Be Ruled Out

Somatic Disorders

Many physical illnesses can cause symptoms similar to those of depression:

• Endocrine disorders: Hypothyroidism, Cushing's syndrome, Addison's disease, diabetes.
• Neurological disorders: Parkinson's disease, multiple sclerosis, stroke, dementia.
• Cancer: Specifically, cancers of the pancreas, lungs, and brain.
• Autoimmune diseases: Systemic lupus erythematosus, rheumatoid arthritis.

Mental Disorders

• Bipolar disorder: It is essential to rule out a history of manic or hypomanic episodes.
• Anxiety disorders: They often co-occur with depression, but they can also be confused with it.
• Personality Disorders: Borderline personality disorder, in particular, can be mistaken for depression.
• Substance-use disorders: They can cause depressive symptoms or co-occur with depression.
• Grief: A normal reaction to loss can be mistaken for depression

Suicide Risk Assessment

Any diagnosis of depression must include a detailed assessment of suicide risk. The specialist should ask directly about:

• Suicidal thoughts (frequency, intensity)
• Suicidal plans (specificity, availability of means)
• Previous suicide attempts
• Risk factors (social isolation, substance abuse, impulsivity)
• Protective factors (social support, family responsibilities, religious beliefs)

Diagnostic Challenges

Masked Depression

Some patients primarily exhibit somatic symptoms, downplaying or failing to recognize their emotional symptoms. This can lead to a delayed diagnosis and unnecessary medical tests.

High-functioning depression

Patients who appear to function normally at work and in their relationships but are internally suffering from symptoms of depression. They often do not seek help on their own or downplay their symptoms.

Comorbidity with Other Disorders

The presence of other mental disorders can complicate the diagnosis and require a comprehensive assessment of all symptoms.

Cultural Differences

The way depression is expressed and experienced may vary across cultures, which requires cultural sensitivity on the part of the professional.

Treatment of Depression—An Evidence-Based Approach

The treatment of depression has undergone a revolution in recent decades, shifting from intuitive approaches to evidence-based medicine. Modern treatment for depression is based on three main pillars: pharmacotherapy, psychotherapy, and psychosocial interventions, which are often used in combination to achieve optimal results.

Pharmacotherapy

• Selective serotonin reuptake inhibitors (SSRIs) are the first-line pharmacological treatment for depression due to their favorable efficacy and safety profile.
• Serotonin and norepinephrine reuptake inhibitors (SNRIs) — are particularly effective in cases of depression accompanied by pain symptoms.
• Tricyclic antidepressants (TCAs)—although older—are still used to treat certain forms of depression.
• Ketamine and esketamine are considered a breakthrough in the treatment of depression. Both substances are NMDA (N-methyl-D-aspartate) receptor antagonists in the brain. Research suggests that ketamine also acts on opioid and GABA receptors and neural transmission pathways, which may modulate brain plasticity and improve neuronal function.

Psychotherapy

Cognitive-behavioral therapy (CBT) is the most extensively studied form of psychotherapy for treating depression and is considered the gold standard. This approach assumes that depression stems from negative thought patterns and maladaptive behaviors that can be identified and changed.

Although psychodynamic therapy has been less extensively studied than CBT, it can be effective, particularly in long-term therapy. This approach holds that depression stems from unresolved unconscious conflicts and early experiences.

Third-wave therapies—newer therapeutic approaches that are gaining popularity:

• Acceptance and Commitment Therapy (ACT): It focuses on accepting difficult emotions and acting in accordance with one's own values.
• Mindfulness-Based Cognitive Therapy (MBCT): Combines elements of CBT with meditation practices; particularly effective in preventing relapses.
• Dialectical Behavior Therapy (DBT): Originally developed for borderline personality disorder, but also effective for depression with elements of impulsivity.

Other Treatment Methods

Electroconvulsive therapy (ECT) — this method has one of the highest success rates among treatments, estimated at 70–80%. It involves electrical stimulation of the brain and is performed under anesthesia.

Repetitive transcranial magnetic stimulation (rTMS)—a noninvasive method of brain stimulation—involves stimulating specific areas of the cerebral cortex using magnetic pulses.

Vagus nerve stimulation (VNS) – an invasive procedure involving the implantation of a stimulator. Electrical stimulation of the vagus nerve affects the areas of the brain responsible for mood.

Deep brain stimulation (DBS) – an experimental treatment for the most severe cases. It involves implanting electrodes into deep brain structures. The method is currently in the clinical trial phase.

Measures to Support the Treatment of Depression

• Physical activity and regular exercise have a proven antidepressant effect. Physical activity works by increasing the production of endorphins, which improves the brain's neuroplasticity.
• Diet – A well-balanced diet can effectively support the treatment of depression. Omega-3 fatty acids, found in fatty ocean fish such as salmon and herring, are particularly important because they support brain function and may alleviate symptoms of depression. B vitamins are also important, especially folate, which is found in leafy green vegetables, eggs, and whole-grain products. Your daily diet should also include minerals such as iron, zinc, and selenium, which can be found in meat, fish, legumes, and eggs. All of these nutrients support the proper functioning of the nervous system, help reduce tension and stress, and can therefore have a positive effect on your mood.

• Sleep hygiene—maintaining a regular circadian rhythm with adequate sleep.
• Light therapy—particularly effective for seasonal depression

In conclusion

Depression is a serious challenge, but it’s not a death sentence. With the right help and treatment, it’s possible not only to overcome the symptoms but also to rebuild a full, fulfilling life. Every day without depression is a victory worth celebrating.

If this guide has helped you better understand the nature of depression or encouraged you to seek help, then it has already achieved its goal. Remember—you are not alone in this struggle, and help is available.

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Bibliography

[1] Marx, W. et al. Major depressive disorder. Nature Reviews Disease Primers 9, 44 (2023). https://www.nature.com/articles/s41572-023-00454-1

[2] Bains, N. & Abdijadid, S. Major Depressive Disorder. StatPearls [Internet]. NCBI Bookshelf (2023). https://www.ncbi.nlm.nih.gov/books/NBK559078/

[3] Mayo Clinic. Depression (major depressive disorder) – Symptoms and causes. https://www.mayoclinic.org/diseases-conditions/depression/symptoms-causes/syc-20356007

[4] Pacjent.gov.pl. When Sadness Is an Illness. https://pacjent.gov.pl/jak-zyc-z-choroba/kiedy-smutek-jest-choroba

[5] Forum Against Depression. Depression – Basic Information. https://forumprzeciwdepresji.pl/932/depresja-podstawowe-informacje