Depression
Symptoms, Causes & Treatment
Everything you need to know about depression: what causes it, how it is diagnosed, and the effective treatments available.
What Is Depression?
Depression is one of the most common mental health conditions in the world, affecting an estimated 280 million people globally and around 3 million people in the UK at any given time. Despite its prevalence, it remains widely misunderstood – often minimised as simply feeling sad or low, when in reality clinical depression is a serious medical condition that affects how a person thinks, feels, and functions across every area of their life.
Depression, formally known as major depressive disorder (MDD) or clinical depression, is characterised by persistent low mood or loss of interest and pleasure that lasts for at least two weeks and significantly impairs daily functioning. It is not a character flaw, a sign of weakness, or something a person can simply "snap out of." It is a medical condition with recognised neurobiological underpinnings, evidence-based treatments, and a good prognosis when properly managed.
Depression exists on a spectrum. Mild depression causes some impairment to daily functioning but allows most activities to continue. Moderate depression significantly disrupts daily life. Severe depression can be debilitating and may be accompanied by psychotic features (such as delusions or hallucinations) or significant risk of self-harm or suicide.
Several related conditions fall within the depressive spectrum: persistent depressive disorder (dysthymia) is a chronic, lower-level form of depression lasting two or more years; seasonal affective disorder (SAD) is characterised by depressive episodes that follow a seasonal pattern, typically worsening in autumn and winter; postnatal depression affects approximately 1 in 10 women following childbirth; and bipolar disorder involves alternating episodes of depression and mania or hypomania (covered separately).
What Are the Symptoms of Depression?
Depression affects mood, thinking, physical health, and behaviour. Symptoms must be present for at least two weeks and represent a change from a person’s normal functioning to meet the clinical threshold for diagnosis.
- Persistent low mood or sadness lasting most of the day, nearly every day
- Loss of interest or pleasure in activities previously enjoyed (anhedonia)
- Fatigue and low energy
- Feelings of worthlessness, guilt, or hopelessness
- Difficulty concentrating, remembering, or making decisions
- Changes in appetite or weight (increased or decreased)
- Sleep disturbance — insomnia or oversleeping
- Moving or speaking more slowly than usual, or feeling agitated and restless
- Recurrent thoughts of death or dying
- Thoughts of self-harm or suicide
- Inability to carry out basic daily tasks such as washing, eating, or leaving the house
- Complete social withdrawal
- Psychotic features: hallucinations or delusions in severe cases
- Symptoms persisting for two weeks or more with significant functional impairment
If you or someone you know is experiencing thoughts of suicide or self-harm, please seek help immediately. Call 999 or go to A&E if there is immediate danger. The Samaritans are available 24 hours a day on 116 123. NHS urgent mental health support is also available via 111. You are not alone — help is available.
What Causes Depression?
Depression does not have a single cause. It arises from a complex interaction of biological, psychological, and social factors. Understanding the contributing factors is an important part of finding the most effective treatment approach.
Depression is associated with dysregulation of neurotransmitters — particularly serotonin, dopamine, and noradrenaline — and structural and functional changes in brain regions involved in mood regulation, including the prefrontal cortex, hippocampus, and amygdala.
Depression has a significant heritable component. Having a first-degree relative with depression increases lifetime risk by two to three times. However, genetics alone do not determine outcome — environmental factors play an equally important role.
Stressful or traumatic life events — including bereavement, relationship breakdown, job loss, financial hardship, abuse, or childhood trauma — are among the most common triggers for a depressive episode, particularly in those with underlying vulnerability.
Chronic illnesses including hypothyroidism, diabetes, heart disease, chronic pain, and cancer are strongly associated with depression. Some medications — including corticosteroids, beta-blockers, and certain hormonal treatments — can also contribute.
Excessive alcohol and drug use can trigger or worsen depression. Alcohol is a central nervous system depressant; while it may temporarily relieve distress, it disrupts sleep, depletes neurotransmitters, and significantly worsens mood over time.
Social isolation, lack of meaningful relationships, unemployment, financial insecurity, and exposure to discrimination or inequality all substantially increase the risk of depression and can perpetuate existing episodes.
Key Risk Factors
How Is Depression Diagnosed?
There is no blood test or scan that can diagnose depression. Diagnosis is made clinically by a GP or mental health professional through a structured interview and validated symptom questionnaires. The PHQ-9 is the most widely used tool in UK primary care and scores the nine core symptoms of depression to determine severity.
How Is Depression Treated?
Treatment is guided by the severity of depression and the individual’s preferences. NICE guidelines recommend a stepped-care approach — starting with the least intensive effective intervention and stepping up if needed. Psychological therapies and antidepressant medication are both effective, and a combination is often more effective than either alone for moderate to severe depression.
Supportive Measures
Alongside formal treatment, a number of self-care measures meaningfully support recovery. Regular physical activity — even light walking — has strong evidence for improving mood. Maintaining a consistent sleep routine, eating regularly, reducing alcohol, and staying connected with supportive people all contribute. Structured self-help programmes and apps can also provide useful support between appointments. Recovery often involves setbacks; being patient with the process and maintaining contact with your clinician is important.
Recurrent & Treatment-Resistant Depression
Around half of people who have one episode of depression will have another. Recurrent depression — defined as two or more depressive episodes — may require longer-term treatment and closer monitoring. Treatment-resistant depression, where symptoms do not adequately respond to two or more antidepressants at adequate doses, affects around one in three people with depression. Options in this case include augmentation strategies (adding a second medication), switching to a different class of antidepressant, specialist psychotherapy, or referral to a psychiatrist for further evaluation including, in some cases, electroconvulsive therapy (ECT) or newer treatments such as esketamine nasal spray.
When Should You Seek Medical Advice for Depression?
You or someone you know is in immediate danger of suicide or self-harm · A person has made a serious attempt to harm themselves · There is a complete inability to care for oneself or others, particularly if children are involved · Psychotic symptoms are present: hallucinations, delusions, or severe agitation.
You have been experiencing persistent low mood, loss of interest, or other depressive symptoms for two weeks or more · Symptoms are worsening despite self-help measures · You are having passive thoughts of death or not wanting to be alive · Depression is affecting your ability to work, care for yourself, or maintain relationships · You are pregnant or have recently given birth and are experiencing low mood or anxiety · A current antidepressant does not seem to be working or is causing side effects.
How Can You Protect Your Mental Health?
While not all episodes of depression can be prevented — particularly where there is a strong biological or genetic component — a number of evidence-based strategies meaningfully reduce the risk of developing depression or experiencing a relapse.
Regular physical activity is one of the most evidence-based interventions for both preventing and treating depression. Even 30 minutes of moderate exercise three to five times per week produces measurable improvements in mood, sleep, and energy through multiple neurobiological mechanisms.
Poor sleep both contributes to and worsens depression. Establishing a consistent sleep schedule, limiting screen time before bed, and avoiding alcohol in the evening all support better sleep quality and mood stability.
Strong social connections are one of the most protective factors against depression. Maintaining regular contact with friends and family, joining community groups, or volunteering can provide purpose, belonging, and emotional support.
Mindfulness-Based Cognitive Therapy (MBCT) is recommended by NICE for people with recurrent depression. Regular mindfulness practice builds awareness of negative thought patterns before they escalate into a depressive episode.
Alcohol is a depressant and significantly worsens mood, sleep, and emotional regulation. Reducing intake — or stopping altogether — can produce rapid and meaningful improvements in mood in people with depression.
Seeking help early — before symptoms become severe — is one of the most important steps. A clinician can offer guidance, therapy referral, or medication before a mild episode becomes a major depressive disorder.
Speak to a Clinician About Depression
Taking the first step towards getting help for depression can feel difficult. Through The GP Service, you can speak to a licensed clinician in a private, confidential online consultation — from home, at a time that suits you. A clinician can assess your symptoms, discuss your options, and refer you for talking therapy or prescribe medication where appropriate.
Expert clinical advice, when you need it.
Depression FAQs
Depression is a clinical condition characterised by persistent low mood, loss of interest or pleasure, and a range of physical and psychological symptoms that last for at least two weeks and significantly impair functioning. It is not the same as ordinary sadness or grief, which are normal responses to difficult events and typically lift over time. Depression persists regardless of circumstances, affects all areas of life, and often cannot simply be overcome with willpower. It is a recognised medical condition with effective, evidence-based treatments.
Treatment for depression is tailored to severity. For mild depression, structured self-help, behavioural activation, and exercise are recommended as first steps. For moderate depression, CBT (Cognitive Behavioural Therapy) and antidepressant medication — most commonly an SSRI such as sertraline — are both effective, and a combination may work best. For severe depression, medication is typically recommended alongside psychological therapy, and specialist referral may be needed. A clinician will discuss the options with you and support you in making the right choice.
Antidepressants are not addictive in the conventional sense — they do not cause cravings or compulsive use. However, stopping them abruptly can cause discontinuation symptoms including dizziness, nausea, and flu-like feelings. This is why they should always be withdrawn gradually under clinical guidance. The decision to start or stop antidepressants should be made collaboratively with a clinician based on your individual circumstances.
Antidepressants typically take four to eight weeks to produce their full therapeutic effect. Some people notice early improvements in sleep and energy within the first two weeks, but mood and motivation often take longer to improve. It is important to continue taking antidepressants as prescribed during this period even if improvement seems slow. If there is no response after four to six weeks at an adequate dose, a clinician may suggest adjusting the dose or switching medication.
NICE recommends continuing antidepressants for at least six months after full remission from a first depressive episode, as stopping too soon significantly increases the risk of relapse. For people who have had two or more episodes, longer-term treatment — sometimes several years — may be recommended. The decision to stop should always be made gradually and in discussion with a clinician, never abruptly.
Yes. Postnatal depression (PND) affects approximately one in ten women in the year after childbirth, and can also affect partners. It goes beyond the ‘baby blues’ — a brief period of tearfulness in the first week after birth — and involves persistent low mood, anxiety, exhaustion, and difficulty bonding with the baby. It is treatable with therapy, medication, and support. If you are experiencing symptoms of PND, speaking to your GP or health visitor is the most important first step.
If someone you care about seems withdrawn, tearful, hopeless, or is expressing thoughts of self-harm, take it seriously. Encourage them to speak to a clinician or call a helpline. Listen without judgement, avoid minimising their experience, and offer practical support with daily tasks. Do not leave someone alone if they have expressed intent to harm themselves. In an emergency, call 999. You can also contact the Samaritans on 116 123, available 24 hours a day.
If you are having thoughts of suicide or self-harm, please seek help immediately. Call 999 or go to your nearest A&E if you are in immediate danger. You can also call the Samaritans on 116 123 (free, 24 hours), contact your GP for an urgent same-day appointment, or call NHS 111. You are not alone, and effective help is available. These thoughts are a symptom of a treatable illness — not a reflection of your worth or your future.