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Depression is more than sadness. It is a legitimate health condition that affects mood, thinking, sleep, appetite, energy, and daily functioning. For many people, symptoms persist despite not having a clear reason, and they can fluctuate in intensity over weeks or months. Understanding depression as a medical condition helps reduce stigma and encourages people to seek appropriate help.

Symptoms of major depressive disorder

Major depressive disorder (MDD) involves a cluster of persistent symptoms that interfere with daily life. To be diagnosed, a clinician typically looks for at least five of the following symptoms over a two-week period, with at least one being a depressed mood or a loss of interest or pleasure:

  • Persistent feelings of sadness, emptiness, or hopelessness
  • Markedly diminished interest or pleasure in most activities
  • Significant weight change or change in appetite
  • Sleep disturbances (insomnia or sleeping too much)
  • fatigue or loss of energy
  • Feelings of worthlessness or excessive guilt
  • Difficulty thinking, concentrating, or making decisions
  • Recurrent thoughts of death or suicide, or a suicide plan
  • Psychomotor agitation or retardation (restlessness or slowed movements)

Symptoms can vary by person and may appear as irritability, physical pain, or social withdrawal, especially in teenagers and older adults. Depression can occur alongside other medical or mental health conditions, which is why a careful evaluation is essential.

Different types of depression

  • Major depressive disorder (MDD): Recurrent, discrete episodes of deep sadness or loss of interest, lasting weeks or longer.
  • Persistent depressive disorder (dysthymia): Long-lasting low mood that lasts most of the day for most days over two years or more, with fewer symptoms than MDD.
  • Seasonal affective disorder (SAD): Depression with a seasonal pattern, typically in fall and winter, often linked to reduced daylight.
  • Postpartum depression: Depression that begins after childbirth, affecting mood, energy, and bonding with the baby; it can occur anytime within the first year after birth.
  • Bipolar depression: Depressive episodes that occur within bipolar I or II disorder, alternating with periods of elevated mood (mania or hypomania).
  • Other specified and unspecified depressive disorders: Depression that doesn’t fit neatly into the above categories but still causes distress or impairment.

Understanding the type helps guide treatment, as some forms respond differently to therapy, medications, or light exposure. For trusted overviews, see resources from NIMH or the Mayo Clinic.

Causes and risk factors

Depression typically arises from a combination of biological, psychological, and environmental factors. There is no single cause, and risk can vary by person.

  • Biological factors: Genetic predisposition; imbalances in brain chemicals (neurotransmitters) that regulate mood; changes in brain structure or function. Some people have a family history that increases risk.
  • Medical and biological contributors: Chronic illnesses (such as diabetes, heart disease, thyroid disorders), chronic pain, sleep disorders, or certain medications can contribute to depressive symptoms.
  • Environmental and life experiences: Trauma, abuse, loss, financial stress, social isolation, and major life transitions can trigger or worsen depression.
  • Psychological factors: Low self-esteem, pessimistic thinking, and certain personality traits can interact with stressors to influence risk.

Protective factors—such as supportive relationships, regular physical activity, healthy sleep, and access to care—can help reduce risk and support recovery. For more on how biology and environment interact, see resources from the National Institute of Mental Health.

Diagnosis process

Depression is diagnosed through a careful clinical evaluation rather than a single lab test. A clinician will typically:

  • Conduct a thorough interview about mood, behavior, daily functioning, and symptom duration
  • Ask about medical history, other mental health conditions, substance use, and risk of self-harm
  • Use standardized screening tools, such as questionnaires like the PHQ-9, to quantify symptom severity
  • Consider possible medical causes and rule out alternatives (for example, thyroid problems or vitamin deficiencies)
  • Assess the impact of symptoms on work, school, relationships, and daily tasks

Diagnosis is guided by diagnostic criteria set forth in manuals such as the DSM-5 or ICD-11. A clinician may adjust the diagnosis as symptoms change over time or in response to treatment. If you’re concerned about depression, starting with a primary care physician or a licensed mental health professional is a good step.

Treatment options

Treatment is most effective when tailored to the individual and may involve one or more of the following approaches:

  • Psychotherapy (talk therapy): Evidence-based approaches include cognitive-behavioral therapy (CBT), interpersonal therapy (IPT), and psychodynamic therapy. Therapy can help you identify unhelpful thinking patterns, cope with stress, improve relationships, and develop healthier routines.
  • Medication: Antidepressants (such as selective serotonin reuptake inhibitors, SNRIs, bupropion, and others) can help correct chemical imbalances and reduce symptoms. It may take several weeks to notice benefits, and a clinician will monitor for side effects and interactions.
  • Combination therapy: Many people benefit from a combination of psychotherapy and medication, especially for moderate to severe depression or when depression is recurrent.
  • Lifestyle and self-care: Regular exercise, balanced nutrition, consistent sleep, limiting alcohol, and stress management can support treatment response and overall well-being.
  • Specialized treatments: For treatment-resistant depression, options such as electroconvulsive therapy (ECT) or transcranial magnetic stimulation (TMS) may be explored with a healthcare professional. Light therapy is often used for seasonal depression.

If you’re considering medication or therapy, discuss goals, potential side effects, and progress with a qualified clinician. For authoritative guidance on treatments, you can consult resources from NIMH or reputable medical centers.

The importance of professional help and available support

Seeking professional help is a critical step toward recovery. A mental health professional can provide diagnosis, monitor safety, tailor treatment, and help you navigate challenges. If you or a loved one is in immediate danger, contact local emergency services or a crisis line.

In the United States, the 988 Lifeline offers 24/7 confidential support for people in distress, or those seeking help for someone else. You can call or text 988 or visit 988lifeline.org for resources and chat options. For ongoing support, consider connecting with local community mental health centers, primary care doctors, or a psychologist, psychiatrist, or social worker.

Support networks, including family, friends, and peer groups, can provide validation and encouragement. If you’re worried about a friend or family member, gentle check-ins, avoiding judgment, and offering help with practical steps (like attending appointments or handling transportation) can make a difference. Learn more about mental health services and support options at NAMI or MentalHealth.gov.

Further resources

If you’re in another country, check your government health department or local nonprofit organizations for regional hotlines and services. Access to timely, professional care improves outcomes and supports lasting recovery.

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