Overview
Depression, also called major depressive disorder, is a common but serious mental health condition that causes persistent sadness or loss of interest in activities, affecting how a person feels, thinks, and manages daily life.
Disease Summary
- Category
- Non-Communicable Disease
- Cause
- A complex interaction of genetic, biological, environmental, and psychological factors
- Transmission
- Not applicable; depression is a mental health condition and cannot be spread between people
- Body System
- Nervous System
- Preventable
- Yes
- Curable
- Yes
Symptoms
Common Symptoms
Symptoms of depression must be present for most of the day, nearly every day, for at least two weeks.
Persistent Sadness or Low Mood
Feeling sad, empty, or hopeless most of the day, nearly every day.
Loss of Interest
Reduced interest or pleasure in activities that were once enjoyable.
Changes in Sleep
Sleeping much more or much less than usual.
Fatigue
Persistent low energy or tiredness, even after rest.
Danger Signs
Seek immediate help if any of the following occur.
Thoughts of Self-harm or Suicide
Any thoughts of self-harm or suicide require immediate help from a healthcare provider or emergency services.
Feeling Hopeless or Worthless
Persistent feelings of hopelessness or worthlessness can be a sign of severe depression.
Withdrawal from Others
Pulling away from friends, family, or usual activities for an extended period.
Difficulty Functioning Daily
Being unable to manage work, school, or basic daily tasks needs prompt evaluation.
Diagnosis
Clinical Assessment
Diagnosis is based on a structured conversation about mood, thoughts, and daily functioning over recent weeks.
Screening Questionnaires
Standardized questionnaires can help identify and measure the severity of depressive symptoms.
Physical and Laboratory Evaluation
Blood tests may be used to rule out physical conditions, such as thyroid problems, that can cause similar symptoms.
Laboratory Tests
Thyroid Function Tests
Rules out thyroid problems, which can cause symptoms similar to depression.
Complete Blood Count (CBC)
Can help identify conditions such as anaemia that may contribute to fatigue and low mood.
Vitamin D and B12 Levels
Low levels have been associated with mood symptoms in some people.
Treatment
Psychological Treatment (Talk Therapy)
Structured talk therapy, such as cognitive behavioural therapy, is an effective first-line treatment for depression.
Antidepressant Medication
Medication can be combined with psychological treatment, particularly for moderate to severe depression.
Prevention
Build strong social connections
Maintaining supportive relationships can help protect against depression.
Manage stress effectively
Developing healthy coping strategies for stress can lower the risk of depressive episodes.
Stay physically active
Regular physical activity is associated with a lower risk of depression.
Seek early support for difficult life events
Getting support after major life changes or losses can help prevent depression from developing or worsening.
Risk Factors
High Risk
These factors substantially increase the likelihood of developing depression.
- Previous episode of depression
- Family history of depression
- Major stressful or traumatic life events
Increased Risk
These factors are associated with a moderately higher risk of depression.
- Chronic physical illness
- Substance use
- Significant social isolation
Additional Contributing Factors
Other factors linked with an increased likelihood of depression.
- Hormonal changes, including during and after pregnancy
- Low socioeconomic status
- Certain medications
Complications
Suicidal Thoughts and Behaviour
People with depression are at increased risk of suicidal thoughts, making early treatment and support especially important.
Worsening of Physical Health Conditions
Depression is linked to a higher risk of conditions such as heart disease and diabetes.
Difficulty Maintaining Relationships and Work
Untreated depression can strain relationships and reduce the ability to work or study effectively.
When to Seek Medical Care
Thoughts of Self-harm or Suicide
Seek immediate help from a healthcare provider, a trusted person, or emergency and crisis services.
Symptoms Lasting More Than Two Weeks
Persistent low mood or loss of interest lasting two weeks or more should be evaluated by a healthcare provider.
Difficulty Functioning
Being unable to manage daily responsibilities is a sign that professional support is needed.
Worsening Symptoms Despite Treatment
Symptoms that do not improve, or that worsen, while receiving treatment should be discussed with a healthcare provider.
Prognosis
Good with Appropriate Treatment
Most people with depression see significant improvement with psychological treatment, medication, or both.
Risk of Recurrence
Depression can recur, particularly in people who have had previous episodes, making ongoing support valuable.
Improved Long-term Outlook with Early Treatment
Early diagnosis and treatment are associated with better long-term outcomes.
Differential Diagnosis
Bipolar Disorder
Involves depressive episodes alternating with periods of mania or hypomania, distinguishing it from depression alone.
Thyroid Disorders
An underactive thyroid can cause fatigue, low mood, and other symptoms that resemble depression.
Grief
Normal grief after a loss can share features with depression but typically follows a different course.
Anxiety Disorder
Can occur alongside or resemble depression, since both involve overlapping symptoms such as sleep difficulty and fatigue.
References
World Health Organization (WHO)
WHO fact sheet on the symptoms, causes, and treatment of depression.
National Institute of Mental Health (NIMH)
NIH guidance on depression symptoms, causes, and treatment options.
World Health Organization (WHO), Mental Disorders
WHO fact sheet covering depression within the broader context of mental disorders.
Frequently Asked Questions
Is depression just feeling sad?
No. Depression is different from ordinary sadness; it involves persistent symptoms lasting at least two weeks that significantly affect daily functioning.
Can depression be treated without medication?
Yes. Psychological treatments such as cognitive behavioural therapy are effective on their own for many people, particularly with mild to moderate depression.
Does depression only affect mood?
No. Depression can also affect sleep, appetite, energy, concentration, and physical health.
Can depression come back after treatment?
Yes. Depression can recur, which is why ongoing support and follow-up care are often recommended, especially for people who have had previous episodes.