Causes
Major depression doesn't have a single cause but often results from a combination of biological, psychological, and environmental factors.- Brain Chemistry (Neurotransmitters): Imbalances in neurotransmitters (chemicals that communicate between brain cells), such as serotonin, norepinephrine, and dopamine, are believed to play a role.
- Brain Structure and Function: Research suggests that certain areas of the brain involved in mood, sleep, appetite, and behavior may function differently in people with depression.
- Genetics: Depression often runs in families, suggesting a genetic predisposition.
- Hormonal Changes: Fluctuations in hormones (e.g., during pregnancy, postpartum, menopause, or with thyroid problems) can contribute.
- Personality Traits: People with certain personality traits, such as low self-esteem, being overly dependent, self-critical, or pessimistic, may be more vulnerable.
- Trauma and Stressful Life Events: Significant life events like loss of a loved one, chronic stress, abuse (physical, sexual, emotional), financial problems, or relationship difficulties can trigger depression.
- Medical Conditions and Medications: Chronic illnesses (e.g., cancer, heart disease, diabetes) and certain medications can be associated with depression.
Symptoms
Symptoms of major depression must last for at least two weeks and represent a change from your previous functioning. They can include:- Depressed mood: Feeling sad, empty, tearful, or hopeless most of the day, nearly every day.
- Loss of interest or pleasure (Anhedonia): A markedly diminished interest or pleasure in all, or almost all, activities most of the day, nearly every day.
- Significant weight changes: Unintentional weight loss or gain, or a decrease or increase in appetite nearly every day.
- Sleep disturbances: Insomnia (difficulty sleeping) or hypersomnia (sleeping too much) nearly every day.
- Psychomotor agitation or retardation: Restlessness or slowed movements and speech, observable by others.
- Fatigue or loss of energy: Feeling tired or lacking energy nearly every day.
- Feelings of worthlessness or excessive/inappropriate guilt: Nearly every day.
- Diminished ability to think or concentrate: Or indecisiveness, nearly every day.
- Recurrent thoughts of death or suicide: Suicidal ideation, a suicide plan, or a suicide attempt.
Diagnosis
Diagnosing major depression involves a comprehensive evaluation by a healthcare professional (e.g., psychiatrist, psychologist, primary care physician). There isn't a single medical test for depression.- Psychiatric evaluation: A detailed interview to understand your symptoms, their duration, severity, and impact on your daily life. The professional will also ask about your personal and family medical and psychiatric history.
- Physical exam and lab tests: To rule out other medical conditions (e.g., thyroid problems, vitamin deficiencies, anemia) that can cause similar symptoms.
- Symptom checklists and rating scales: Standardized questionnaires (e.g., PHQ-9, Beck Depression Inventory) may be used to assess the severity of depressive symptoms.
- Diagnostic criteria: Symptoms must meet specific criteria outlined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5).
Treatment
Treatment for major depression is highly effective for most people and often involves a combination of psychotherapy, medication, and lifestyle adjustments.- Psychotherapy (Talk Therapy):
- Cognitive Behavioral Therapy (CBT): Helps identify and change negative thought patterns and behaviors that contribute to depression.
- Interpersonal Therapy (IPT): Focuses on improving relationship problems and social functioning.
- Psychodynamic Therapy: Explores unconscious conflicts and past experiences.
- Medication (Antidepressants):
- Selective Serotonin Reuptake Inhibitors (SSRIs): Often the first-line choice (e.g., fluoxetine, sertraline, escitalopram). They increase serotonin levels in the brain.
- Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs): Increase both serotonin and norepinephrine (e.g., duloxetine, venlafaxine).
- Atypical Antidepressants: Work differently than SSRIs/SNRIs (e.g., bupropion, mirtazapine).
- Tricyclic Antidepressants (TCAs) and Monoamine Oxidase Inhibitors (MAOIs): Older antidepressants, potent but with more side effects, usually reserved for when other treatments are ineffective.
- Brain Stimulation Therapies (for severe or treatment-resistant depression):
- Electroconvulsive Therapy (ECT): Involves passing small electrical currents through the brain to trigger a brief seizure. Highly effective for severe depression.
- Transcranial Magnetic Stimulation (TMS): Uses magnetic fields to stimulate nerve cells in the brain. Non-invasive.
- Vagus Nerve Stimulation (VNS): A device is surgically implanted to stimulate the vagus nerve.
- Lifestyle Management:
- Regular Exercise: Can improve mood and reduce depressive symptoms.
- Healthy Diet: Balanced nutrition supports overall brain health.
- Adequate Sleep: Establishing a consistent sleep schedule.
- Stress Management: Techniques like mindfulness, meditation, and yoga.
- Avoiding Alcohol and Recreational Drugs: These can worsen depression.
- Social Support: Connecting with friends, family, or support groups.
Getting Treatment to Work
Depression is among the most treatable conditions in medicine, and also among the most often undertreated, because the first attempt frequently falls short and nobody adjusts it. The difference between treatment that works and treatment that does not is usually follow-up.
The first antidepressant is a starting point
Roughly a third of people reach full remission on the first antidepressant and about half respond partially. That is expected, not failure. Symptoms are tracked with a short questionnaire every four to six weeks; a partial response at four weeks prompts a dose increase, and little response at eight prompts a switch or an added medication. Sertraline and escitalopram are common first choices, bupropion avoids sexual side effects and weight gain, and trazodone at low dose helps when insomnia dominates.
Side effects that lead people to quit, and what to do instead
Nausea and headache in the first two weeks usually pass. Sexual side effects and emotional flatness do not, and they are the commonest reasons people stop; switching to a different class fixes them more often than not. Stopping abruptly, especially venlafaxine or paroxetine, causes dizziness, electric-shock sensations, and irritability that are mistaken for relapse, so any change is tapered.
How long to continue once you feel well
The medication is continued for at least six to twelve months after remission for a first episode, and often indefinitely after three or more episodes, because the relapse rate on stopping early is high. Feeling well is the treatment working. Therapy, particularly cognitive behavioral therapy and behavioral activation, adds to medication in moderate and severe depression and reduces the chance of relapse after it ends.
Depression that is something else
Hypothyroidism, vitamin B12 deficiency, sleep apnea, and heavy alcohol use all present as depression and do not respond to antidepressants. So does bipolar disorder, where an antidepressant alone can trigger mania, which is why a history of unusually elevated mood is asked about before treatment begins. In older adults, grief and depression are confused in both directions; our grief versus depression article draws the line.
When it cannot wait
Thoughts of not wanting to be alive, or of harming yourself, need same-day contact, not a routine appointment. The 988 Suicide and Crisis Lifeline is available by call or text around the clock. Our behavioral health team manages depression in primary care and coordinates referral for treatment-resistant illness. The NIMH and the 988 Lifeline provide patient guidance and immediate support.
If you have been on an antidepressant for more than two months without clear improvement, or stopped one because of side effects, schedule a visit; there are more options than the first one.